The Eastern Orthodox Church, officially the Orthodox Catholic Church,^{[7][8][9][10]} is the second-largest Christian church, with approximately 260 million baptised members.^{[6][11][12][13][14]} It operates as a communion of autocephalous churches, each governed by its bishops in local synods.^[13] Roughly half of Eastern Orthodox Christians live in Russia. The church has no central doctrinal or governmental authority analogous to the Bishop of Rome, but the Ecumenical Patriarch of Constantinople is recognised by all as primus inter pares ("first among equals") of the bishops. As one of the oldest surviving religious institutions in the world, the Eastern Orthodox Church has played a prominent role in the history and culture of Eastern and Southeastern Europe, the Caucasus, and the Near East.^[15]

Eastern Orthodox theology is based on the Nicene-Constantinopolitan Creed (known simply as the Nicene Creed). The church teaches that it is the One, Holy, Catholic and Apostolic church established by Jesus Christ in his Great Commission, and that its bishops are the successors of Christ's apostles.^[16] It maintains that it practices the original Christian faith, as passed down by holy tradition. Its patriarchates, reminiscent of the pentarchy, and autocephalous and autonomous churches reflect a variety of hierarchical organisation. Of its innumerable sacred mysteries, it recognises seven major sacraments, of which the Eucharist is the principal one, celebrated liturgically in synaxis. The church teaches that through consecration invoked by a priest, the sacrificial bread and wine become the body and blood of Christ. The Virgin Mary is venerated in the Eastern Orthodox Church as the God-bearer, honoured in devotions.

The Eastern Orthodox Church shared communion with the Roman Catholic Church until the East–West Schism in 1054, disputing particularly the authority of the Pope. Before the Council of Ephesus in AD 431 the Church of the East also shared in this communion, as did the Oriental Orthodox churches before the Council of Chalcedon in AD 451, all separating primarily over differences in Christology.

The majority of Eastern Orthodox Christians live mainly in Southeast and Eastern Europe, Cyprus, Georgia and other communities in the Caucasus region, and communities in Siberia reaching the Russian Far East. There are also smaller communities in the former Byzantine regions of Africa, the Eastern Mediterranean, and in the Middle East where it is decreasing due to forced migration because of increased religious persecution in recent years.^[17][18] There are also many in other parts of the world, formed through diaspora, conversions, and missionary activity.

In keeping with the church's teaching on universality and with the Nicene Creed, Orthodox authorities such as Saint Raphael of Brooklyn have insisted that the full name of the church has always included the term "Catholic", as in "Holy Orthodox Catholic Apostolic Church".^[19][20][21] The official name of the Eastern Orthodox Church is the "Orthodox Catholic Church".^{[7][8][9][10]} It is the name by which the church refers to itself in its liturgical or canonical texts,^{[22][23][24][25][26][27][28][29]} in official publications,^[30][31] and in official contexts or administrative documents.^[32][33] Orthodox teachers refer to the church as Catholic.^[34][35] This name and longer variants containing "Catholic" are also recognised and referenced in other books and publications by secular or non-Orthodox writers.^{[36][37][38][39][40][41]}

The common name of the church, "Eastern Orthodox Church", is a shortened practicality that helps to avoid confusions in casual use. From ancient times through the first millennium, Greek was the most prevalent shared language in the demographic regions where the Byzantine Empire flourished, and Greek, being the language in which the New Testament was written, was the primary liturgical language of the church. For this reason, the eastern churches were sometimes identified as "Greek" (in contrast to the "Roman" or "Latin" church, which used a Latin translation of the Bible), even before the Great Schism of 1054. After 1054, "Greek Orthodox" or "Greek Catholic" marked a church as being in communion with Constantinople, much as "Catholic" did for communion with Rome. This identification with Greek, however, became increasingly confusing with time. Missionaries brought Orthodoxy to many regions without ethnic Greeks, where the Greek language was not spoken. In addition, struggles between Rome and Constantinople to control parts of Southeastern Europe resulted in the conversion of some churches to Rome, which then also used "Greek Catholic" to indicate their continued use of the Byzantine rites. Today, many of those same churches remain, while a very large number of Orthodox are not of Greek national origin, and do not use Greek as the language of worship.^[42] "Eastern", then, indicates the geographical element in the Church's origin and development, while "Orthodox" indicates the faith, as well as communion with the Ecumenical Patriarchate of Constantinople.^[43] There are additional Christian churches in the east that are in communion with neither Rome nor Constantinople, who tend to be distinguished by the category named "Oriental Orthodox". While the church continues officially to call itself "Catholic", for reasons of universality, the common title of "Eastern Orthodox Church" avoids casual confusion with the Roman Catholic Church.

The first known use of the phrase "the catholic Church" (he katholike ekklesia) occurred in a letter written about 110 AD from one Greek church to another (Saint Ignatius of Antioch to the Smyrnaeans). The letter states: "Wheresoever the bishop shall appear, there let the people be, even as where Jesus may be, there is the universal [katholike] Church."^[44] Thus, almost from the very beginning, Christians referred to the Church as the "One, Holy, Catholic (from the Greek καθολική, or "according to the whole, universal") and Apostolic Church".^[45] The Eastern Orthodox Church claims that it is today the continuation and preservation of that same early Church.

A number of other Christian churches also make a similar claim: the Roman Catholic Church, the Anglican Communion, the Assyrian Church and the Oriental Orthodox. In the Eastern Orthodox view, the Assyrians and Orientals left the Orthodox Church in the years following the Third Ecumenical Council of Ephesus (431) and the Fourth Ecumenical Council of Chalcedon (451), respectively, in their refusal to accept those councils' Christological definitions. Similarly, the churches in Rome and Constantinople separated in an event known as the East–West Schism, traditionally dated to the year 1054, although it was more a gradual process than a sudden break. The Church of England separated from the Catholic Church, not directly from the Eastern Orthodox Church, for the first time in the 1530s (and, after a brief reunion in 1555, again finally in 1558). Thus, though it was united to Orthodoxy when established through the work of Saint Augustine of Canterbury in the early 7th century, its separation from Orthodoxy came about indirectly through the See of Rome.

To all these churches, the claim to catholicity (universality, oneness with the ancient Church) is important for multiple doctrinal reasons that have more bearing internally in each church than in their relation to the others, now separated in faith. The meaning of holding to a faith that is true is the primary reason why anyone's statement of which church split off from which other has any significance at all; the issues go as deep as the schisms. The depth of this meaning in the Eastern Orthodox Church is registered first in its use of the word "Orthodox" itself, a union of Greek orthos ("straight", "correct", "true", "right") and doxa ("common belief", from the ancient verb δοκέω-δοκῶ which is translated "to believe", "to think", "to consider", "to imagine", "to assume").^[46]

The dual meanings of doxa, with "glory" or "glorification" (of God by the Church and of the Church by God), especially in worship, yield the pair "correct belief" and "true worship". Together, these express the core of a fundamental teaching about the inseparability of belief and worship and their role in drawing the church together with Christ.^[47][48] The Bulgarian and all the Slavic churches use the title Pravoslavie (Cyrillic: Православие), meaning "correctness of glorification", to denote what is in English Orthodoxy, while the Georgians use the title Martlmadidebeli. Several other churches in Europe, Asia, and Africa also came to use Orthodox in their titles, but are still distinct from the Eastern Orthodox Church as described in this article.

The term "Eastern Church" (the geographic east in the East–West Schism) has been used to distinguish it from western Christendom (the geographic West, which at first came to designate the Catholic communion, later also the various Protestant and Anglican branches). "Eastern" is used to indicate that the highest concentrations of the Eastern Orthodox Church presence remain in the eastern part of the Christian world, although it is growing worldwide. Orthodox Christians throughout the world use various ethnic or national jurisdictional titles, or more inclusively, the title "Eastern Orthodox", "Orthodox Catholic", or simply "Orthodox".^[43]

What unites Orthodox Christians is the catholic faith as carried through holy tradition. That faith is expressed most fundamentally in scripture and worship,^[49] and the latter most essentially through baptism and in the Divine Liturgy.^[50] Orthodox Christians proclaim the faith lives and breathes by God's energies in communion with the church. Inter-communion is the litmus test by which all can see that two churches share the same faith; lack of inter-communion (excommunication, literally "out of communion") is the sign of different faiths, even though some central theological points may be shared. The sharing of beliefs can be highly significant, but it is not the full measure of the faith according to the Orthodox.

The lines of even this test can blur, however, when differences that arise are not due to doctrine, but to recognition of jurisdiction. As the Eastern Orthodox Church has spread into the west and over the world, the church as a whole has yet to sort out all the inter-jurisdictional issues that have arisen in the expansion, leaving some areas of doubt about what is proper church governance.^[51] And as in the ancient church persecutions, the aftermath of persecutions of Christians in communist nations has left behind both some governance and some faith issues that have yet to be completely resolved.^[52]

All members of the Eastern Orthodox Church profess the same faith, regardless of race or nationality, jurisdiction or local custom, or century of birth. Holy tradition encompasses the understandings and means by which that unity of faith is transmitted across boundaries of time, geography, and culture. It is a continuity that exists only inasmuch as it lives within Christians themselves.^[53] It is not static, nor an observation of rules, but rather a sharing of observations that spring both from within and also in keeping with others, even others who lived lives long past. The church proclaims the Holy Spirit maintains the unity and consistency of holy tradition to preserve the integrity of the faith within the church, as given in the scriptural promises.^[54]

The shared beliefs of Orthodoxy, and its theology, exist within Holy Tradition and cannot be separated from it, for their meaning is not expressed in mere words alone.^[55] Doctrine cannot be understood unless it is prayed.^[56] Doctrine must also be lived in order to be prayed, for without action, the prayer is idle and empty, a mere vanity, and therefore the theology of demons.^[57] According to these teachings of the ancient Church, no superficial belief can ever be orthodox. Similarly, reconciliation and unity are not superficial, but are prayed and lived out.

The Eastern Orthodox Church considers itself to be both orthodox and catholic. The doctrine of the Catholicity of the Church, as derived from the Nicene Creed, is essential to Eastern Orthodox ecclesiology. The term Catholicity of the Church (Greek Καθολικότης τῆς Ἐκκλησίας) is used in its original sense, as a designation for the Universality of the Church, centered around Christ. Therefore, the Eastern Orthodox notion of catholicity is not centered around any singular see, unlike Catholicism, that has one earthly center.

Due to the influence of the Catholic Church in the west, where the English language itself developed, the words "catholic" and "catholicity" are sometimes used to refer to that church specifically. However, the more prominent dictionary sense given for general use is still the one shared by other languages, implying breadth and universality, reflecting comprehensive scope.^[58] In a Christian context, the Christian Church, as identified with the original Church founded by Christ and his apostles, is said to be catholic (or universal) in regard to its union with Christ in faith. Just as Christ is indivisible, so are union with him and faith in him, whereby the Church is "universal", unseparated, and comprehensive, including all who share that faith. Orthodox bishop Kallistos Ware has called that "simple Christianity".^[59] That is the sense of early and patristic usage wherein the church usually refers to itself as the "Catholic Church",^[60][61] whose faith is the "Orthodox faith". It is also the sense within the phrase "One, Holy, Catholic, and Apostolic Church", found in the Nicene Creed, and referred to in Orthodox worship, e.g. in the litany of the catechumens in the Divine Liturgy.

With the mutual excommunications of the East–West Schism in 1054, the churches in Rome and Constantinople each viewed the other as having departed from the true Church, leaving a smaller but still-catholic church in place. Each retained the "Catholic" part of its title, the "Roman Catholic Church" (or Catholic Church) on the one hand, and the "Orthodox Catholic Church" on the other, each of which was defined in terms of inter-communion with either Rome or Constantinople. While the Eastern Orthodox Church recognises what it shares in common with other churches, including the Catholic Church, it sees catholicity in terms of complete union in communion and faith, with the Church throughout all time, and the sharing remains incomplete when not shared fully.

The religious authority for Eastern Orthodoxy is not a patriarch or the Bishop of Rome as in Catholicism, nor the Bible as in Protestantism, but the scriptures as interpreted by the seven ecumenical councils of the Imperial Roman Church. The Eastern Orthodox Church is a fellowship of "autocephalous" (Greek for self-headed) churches, with the Ecumenical Patriarch of Constantinople being the only autocephalous head who holds the title primus inter pares, meaning "first among equals" in Latin. The Patriarch of Constantinople has the honor of primacy, but his title is only first among equals and has no real authority over churches other than the Constantinopolitan,^[62][63][64] though at times the office of the Ecumenical Patriarch has been accused of Constantinopolitan or Eastern papism.^[65][66] The Eastern Orthodox Church considers Jesus Christ to be the head of the church and the church to be his body. It is believed that authority and the grace of God is directly passed down to Orthodox bishops and clergy through the laying on of hands—a practice started by the apostles, and that this unbroken historical and physical link is an essential element of the true Church (Acts 8:17, 1 Tim 4:14, Heb 6:2). The Orthodox Church asserts that apostolic succession requires apostolic faith, and bishops without apostolic faith, who are in heresy, forfeit their claim to apostolic succession.^[67]

The Eastern Orthodox communion is organised into several regional churches, which are either autocephalous ("self-headed") or lower ranking autonomous (the Greek term for "self-lawed") church bodies unified in theology and worship. These include the fourteen autocephalous churches of Constantinople, Alexandria, Antioch, Jerusalem, Georgia, Cyprus, Bulgaria, Serbia, Russia, Greece, Poland, Romania, Albania, and the Czech Republic and Slovakia, which were officially invited to the Pan-Orthodox Council of 2016,^[68] the Orthodox Church in America formed in 1970, the autocephalous Orthodox Church of Ukraine created in 2019, as well as a number of autonomous churches.^[63] Each church has a ruling bishop and a holy synod to administer its jurisdiction and to lead the Orthodox Church in the preservation and teaching of the apostolic and patristic traditions and church practices.

Each bishop has a territory (see) over which he governs.^[64] His main duty is to make sure the traditions and practices of the Orthodox Church are preserved. Bishops are equal in authority and cannot interfere in the jurisdiction of another bishop. Administratively, these bishops and their territories are organised into various autocephalous groups or synods of bishops who gather together at least twice a year to discuss the state of affairs within their respective sees. While bishops and their autocephalous synods have the ability to administer guidance in individual cases, their actions do not usually set precedents that affect the entire Eastern Orthodox Church. Bishops are almost always chosen from the monastic ranks and must remain unmarried.

There have been a number of times when alternative theological ideas arose to challenge the Orthodox faith. At such times the Orthodox communion deemed it necessary to convene a general or "great" council of all available bishops throughout the world. The Orthodox Church holds that seven ecumenical councils, held between the 4th and the 8th centuries, are authoritative.

The ecumenical councils followed a democratic form, with each bishop having one vote. Though present and allowed to speak before the council, members of the Imperial Roman/Byzantine court, abbots, priests, deacons, monks and laymen were not allowed to vote. The primary goal of these great synods was to verify and confirm the fundamental beliefs of the Great Christian Church as truth, and to remove as heresy any false teachings that would threaten the Church. The Pope of Rome at that time held the position of "Primus inter pares" ("first among equals") and, while he was not present at any of the councils, he continued to hold this title until the East–West Schism of 1054.

Other councils have helped to define the Eastern Orthodox position, specifically the Quinisext Council, the Synods of Constantinople, 879–880, 1341, 1347, 1351, 1583, 1819, and 1872, the Synod of Jassy (Iași), 1642, and the Pan-Orthodox Synod of Jerusalem, 1672; the Pan-Orthodox Council, held in Greece in 2016, was the only such Eastern Orthodox council in modern times.

According to Orthodox teaching the position of "first among equals" gives no additional power or authority to the bishop that holds it, but rather that this person sits as organizational head of a council of equals (like a president). His words and opinions carry no more insight or wisdom than any other bishop. It is believed that the Holy Spirit guides the Eastern Orthodox Church through the decisions of the entire council, not one individual. Additionally it is understood that even the council's decisions must be accepted by the entire Orthodox Church in order for them to be valid.

One of the decisions made by the First Council of Constantinople (the second ecumenical council, meeting in 381) and supported by later such councils was that the Patriarch of Constantinople should be given equal honor to the Pope of Rome since Constantinople was considered to be the "New Rome". According to the third canon of the second ecumenical council: "Because it is new Rome, the bishop of Constantinople is to enjoy the privileges of honor after the bishop of Rome." This means that both enjoy the same privileges because they are both bishops of the imperial capitals, but the bishop of Rome will precede the bishop of Constantinople since Old Rome precedes New Rome.

The 28th canon of the fourth ecumenical council clarified this point by stating: "For the Fathers rightly granted privileges to the throne of Old Rome because it was the royal city. And the One Hundred and Fifty most religious Bishops (i.e. the second ecumenical council in 381) actuated by the same consideration, gave equal privileges to the most holy throne of New Rome, justly judging that the city which is honoured with the Sovereignty and the Senate, and enjoys equal privileges with the old imperial Rome, should in ecclesiastical matters also be magnified as she is."

Because of the schism the Eastern Orthodox no longer recognise the primacy of the Pope of Rome. The Patriarch of Constantinople therefore, like the Pope before him, now enjoys the title of "first among equals".

Politics, wars, persecutions, oppressions, and related potential threats^[69] can make precise counts of Orthodox membership difficult to obtain at best in some regions. Historically, forced migrations have also altered demographics in relatively short periods of time. The most reliable estimates currently available number Orthodox adherents at around 200 million worldwide,^[62] making Eastern Orthodoxy the second largest Christian communion in the world after the Catholic Church.^[70] The numerous Protestant groups in the world, if taken all together, outnumber the Eastern Orthodox,^[71] but they differ theologically and do not form a single communion.^[70] According to the 2015 Yearbook of International Religious Demography, the Eastern Orthodox population in 2010 decreased to 4% of the global population from 7.1% of the global population in 1910. According to the same source, in terms of the total Christian population, the relative percentages were 12.2% and 20.4% respectively.^[72] According to the Pew Research Center, the Eastern Orthodox share of the world's total Christian population was 12% in 2011.^{[73] []}

Most members today are concentrated in Eastern Europe and Asian Russia, in addition to significant minorities in Central Asia and the Levant, although Eastern Orthodoxy has spread into a global religion towards Western Europe and the New World, with churches in most countries and major cities. The adherents constitute the largest single religious faith in the world's largest country—Russia,^[74][1] where roughly half of Eastern Orthodox Christians live. They are the majority religion in Ukraine,^[76][77] Romania,^[76] Belarus,^[78] Greece,^[2][76] Serbia,^[76] Bulgaria,^[76] Moldova,^[76] Georgia,^[76] North Macedonia,^[76] Cyprus,^[76] and Montenegro;^[76] they also dominate in the disputed territories of Abkhazia, South Ossetia and Transnistria. Significant minorities of Eastern Orthodox are present in Bosnia and Herzegovina (absolute majority in Republika Srpska),^[76] Latvia,^[79] Estonia,^[80] Kazakhstan,^[81] Kyrgyzstan,^[82] Lebanon,^[83] Albania, Syria,^[76] and many other countries.

The percentage of Christians in Turkey fell from 19 percent in 1914 to 2.5 percent in 1927,^[84] predominantly due to persecution, including the Armenian Holocaust, the Greek genocide and subsequent population exchange between Greece and Turkey,^[85] population exchanges between Bulgaria and Turkey, and associated emigration of Christians to foreign countries (mostly in Europe and the Americas).^[86] Today there are more than 160,000 people (about 0.2%) of different Christian denominations.^[76]

Through mostly labor migration from Eastern Europe and some conversion, Orthodox Christianity is the fastest growing religious grouping in certain Western countries, for example in the Republic of Ireland,^[87][88][89] but Orthodoxy is not "a central marker of minority identity" for the migrants.^[87] While in the United States, the number of Orthodox parishes is growing.^[90][3][4]

Orthodox Christians believe in the Trinity, three distinct, divine persons (hypostases), without overlap or modality among them, who each have one divine essence (ousia Greek οὐσία)—uncreated, immaterial and eternal.^[94] These three persons are typically distinguished by their relation to each other. The Father is eternal and not begotten and does not proceed from any, the Son is eternal and begotten of the Father, and the Holy Spirit is eternal and proceeds from the Father. Orthodox doctrine regarding the Trinity is summarised in the Nicene Creed.^[95]

In discussing God's relationship to his creation, Orthodox theology distinguishes between God's eternal essence, which is totally transcendent, and his uncreated energies, which is how he reaches humanity. The God who is transcendent and the God who touches mankind are one and the same. That is, these energies are not something that proceed from God or that God produces, but rather they are God himself: distinct, yet inseparable from God's inner being.^[96]

In understanding the Trinity as "one God in three persons", "three persons" is not to be emphasised more than "one God", and vice versa. While the three persons are distinct, they are united in one divine essence, and their oneness is expressed in community and action so completely that they cannot be considered separately. For example, their salvation of mankind is an activity engaged in common: "Christ became man by the good will of the Father and by the cooperation of the Holy Spirit. Christ sends the Holy Spirit who proceeds from the Father, and the Holy Spirit forms Christ in our hearts, and thus God the Father is glorified." Their "communion of essence" is "indivisible". Trinitarian terminology—essence, hypostasis, etc.—are used "philosophically", "to answer the ideas of the heretics", and "to place the terms where they separate error and truth."^[97] The words do what they can do, but the nature of the Trinity in its fullness is believed to remain beyond man's comprehension and expression, a holy mystery that can only be experienced.

According to the Eastern Orthodox faith, at some point in the beginnings of human existence, humanity was faced with a choice: to learn the difference between good and evil through observation or through participation. The biblical story of Adam and Eve relates this choice by mankind to participate in evil, accomplished through disobedience to God's command. Both the intent and the action were separate from God's will; it is that separation that defines and marks any operation as sin. The separation from God caused the loss of (fall from) his grace, a severing of mankind from his creator and the source of his life. The end result was the diminishment of human nature and its subjection to death and corruption, an event commonly referred to as the "fall of man".

When Orthodox Christians refer to fallen nature they are not saying that human nature has become evil in itself. Human nature is still formed in the image of God; humans are still God's creation, and God has never created anything evil, but fallen nature remains open to evil intents and actions. It is sometimes said among Orthodox that humans are "inclined to sin"; that is, people find some sinful things attractive. It is the nature of temptation to make sinful things seem the more attractive, and it is the fallen nature of humans that seeks or succumbs to the attraction. Orthodox Christians reject the Augustinian position that the descendants of Adam and Eve are actually guilty of the original sin of their ancestors.^[98] But just as any species begets its own kind, so fallen humans beget fallen humans, and from the beginning of humanity's existence people lie open to sinning by their own choice.

Since the fall of man, then, it has been mankind's dilemma that no human can restore his nature to union with God's grace; it was necessary for God to effect another change in human nature. Orthodox Christians believe that Christ Jesus was both God and Man absolutely and completely, having two natures indivisibly: eternally begotten of the Father in his divinity, he was born in his humanity of a woman, Mary, by her consent, through descent of the Holy Spirit. He lived on earth, in time and history, as a man. As a man he also died, and went to the place of the dead, which is Hades. But being God, neither death nor Hades could contain him, and he rose to life again, in his humanity, by the power of the Holy Spirit, thus destroying the power of Hades and of death itself.^[99] Through God's participation in humanity, Christ's human nature, perfected and unified with his divine nature, ascended into heaven, there to reign in communion with the Father and Holy Spirit.

By these acts of salvation, Christ provided fallen mankind with the path to escape its fallen nature. The Eastern Orthodox Church teaches that through baptism into Christ's death, and a person's death unto sin in repentance, with God's help mankind can also rise with Christ into heaven, healed of the breach of man's fallen nature and restored to God's grace. To Orthodox Christians, this process is what is meant by "salvation," which consists of the Christian life. The ultimate goal is theosis an even closer union with God and closer likeness to God than existed in the Garden of Eden. This process is called Deification or "God became man that man might become 'god'". However, it must be emphasised that Orthodox Christians do not believe that man becomes God in his essence, or a god in his own nature. More accurately, Christ's salvific work enables man in his human nature to become "partakers of the Divine nature" (2 Peter 1:4); that is to say, man is united to God in Christ.

Through Christ's destruction of Hades' power to hold humanity hostage, he made the path to salvation effective for all the righteous who had died from the beginning of time—saving many, including Adam and Eve, who are remembered in the Church as saints.^[100]

The Eastern Orthodox reject the idea that Christ died to give God "satisfaction" as taught by Anselm, or as a punitive substitute as taught by the Reformers. Sin (separation from God, who is the source of all life) is its own punishment, capable of imprisoning the soul in an existence without life, without anything good, and without hope: hell by any measure. Life on earth is God's gift, to give humankind opportunity to make their choice real: separation or union.

The Eastern Orthodox Church understands the death and resurrection of Jesus to be real historical events, as described in the gospels of the New Testament. Jesus Christ, the Son of God, is believed to, according to Orthodox teaching, in his humanity be (that is, in history) crucified, and died, descending into Hades (Sheol), the place of the dead, as all humans do. But he, alone among humans, has two natures, one human, one divine, which are indivisible and inseparable from each other through the mystery of the incarnation. Hades could not restrain the infinite God. Christ in his divine nature captured the keys of Hades and broke the bonds which had imprisoned the human souls who had been held there through their separation from God.

Neither could death contain the Son of God, the Fountain of Life, who arose from death even in his human nature. Not only this, but he opened the gates of Hades to all the righteous dead of past ages, rescuing them from their fallen human nature and restoring them to a nature of grace with God, bringing them back to life, this time in God's heavenly kingdom. And this path he opened to all who choose to follow him in time yet to come, thus saving the human race. Thus the Eastern Orthodox proclaim each year at the time of Pascha (Easter), that Christ "trampled down death by death, and on those in the tombs bestowed life."

The celebration of the Resurrection of Christ at Pascha is the central event in the liturgical year of the Eastern Orthodox Church. According to Orthodox tradition, each human being may partake of this immortality, which would have been impossible without the Resurrection; it is the main promise held out by God in the New Testament. Every holy day of the Eastern Orthodox liturgical year relates to the Resurrection directly or indirectly. Every Sunday is especially dedicated to celebrating the Resurrection and the triune God, representing a mini-Pascha. In the liturgical commemorations of the Passion of Christ during Holy Week there are frequent allusions to the ultimate victory at its completion.

Church teaching is that Orthodox Christians, through baptism, enter a new life of salvation through repentance whose purpose is to share in the life of God through the work of the Holy Spirit. The Eastern Orthodox Christian life is a spiritual pilgrimage in which each person, through the imitation of Christ and hesychasm,^[101] cultivates the practice of unceasing prayer. Each life occurs within the life of the church as a member of the body of Christ.^[102] It is then through the fire of God's love in the action of the Holy Spirit that each member becomes more holy, more wholly unified with Christ, starting in this life and continuing in the next.^[103][104] The church teaches that everyone, being born in God's image, is called to theosis, fulfillment of the image in likeness to God. God the creator, having divinity by nature, offers each person participation in divinity by cooperatively accepting His gift of grace.^[105]

The Eastern Orthodox Church, in understanding itself to be the Body of Christ, and similarly in understanding the Christian life to lead to the unification in Christ of all members of his body, views the church as embracing all Christ's members, those now living on earth, and also all those through the ages who have passed on to the heavenly life. The church includes the Christian saints from all times, and also judges, prophets and righteous Jews of the first covenant, Adam and Eve, even the angels and heavenly hosts.^[106] In Orthodox services, the earthly members together with the heavenly members worship God as one community in Christ, in a union that transcends time and space and joins heaven to earth. This unity of the Church is sometimes called the communion of the saints.^[107]

The Eastern Orthodox Church believes death and the separation of body and soul to be unnatural—a result of the Fall of Man. They also hold that the congregation of the church comprises both the living and the dead. All persons currently in heaven are considered to be saints, whether their names are known or not. There are, however, those saints of distinction whom God has revealed as particularly good examples. When a saint is revealed and ultimately recognised by a large portion of the church a service of official recognition (canonization) is celebrated.

This does not "make" the person a saint; it merely recognises the fact and announces it to the rest of the church. A day is prescribed for the saint's celebration, hymns composed and icons created. Numerous saints are celebrated on each day of the year. They are venerated (shown great respect and love) but not worshipped, for worship is due God alone (this view is also held by the Oriental Orthodox and Catholic Churches). In showing the saints this love and requesting their prayers, the Eastern Orthodox manifest their belief that the saints thus assist in the process of salvation for others.

Pre-eminent among the saints is the Virgin Mary (commonly referred to as Theotokos or Bogoroditsa) ("Mother of God"). In Orthodox theology, the Mother of God is the fulfillment of the Old Testament archetypes revealed in the Ark of the Covenant (because she carried the New Covenant in the person of Christ) and the burning bush that appeared before Moses (symbolizing the Mother of God's carrying of God without being consumed).^[108] Accordingly, the Eastern Orthodox consider Mary to be the Ark of the New Covenant and give her the respect and reverence as such. The Theotokos, in Orthodox teaching, was chosen by God and she freely co-operated in that choice to be the Mother of Jesus Christ, the God-man.

The Eastern Orthodox believe that Christ, from the moment of his conception, was both fully God and fully human. Mary is thus called the Theotokos or Bogoroditsa as an affirmation of the divinity of the one to whom she gave birth. It is also believed that her virginity was not compromised in conceiving God-incarnate, that she was not harmed and that she remained forever a virgin. Scriptural references to "brothers" of Christ are interpreted as kin, given that the word "brother" was used in multiple ways, as was the term "father". Due to her unique place in salvation history, Mary is honoured above all other saints and especially venerated for the great work that God accomplished through her.^[109]

The Eastern Orthodox Church regards the bodies of all saints as holy, made such by participation in the holy mysteries, especially the communion of Christ's holy body and blood, and by the indwelling of the Holy Spirit within the church. Indeed, that persons and physical things can be made holy is a cornerstone of the doctrine of the Incarnation, made manifest also directly by God in Old Testament times through his dwelling in the Ark of the Covenant. Thus, physical items connected with saints are also regarded as holy, through their participation in the earthly works of those saints. According to church teaching and tradition, God himself bears witness to this holiness of saints' relics through the many miracles connected with them that have been reported throughout history since Biblical times, often including healing from disease and injury.^[110]

Orthodox Christians believe that when a person dies the soul is temporarily separated from the body. Though it may linger for a short period on Earth, it is ultimately escorted either to paradise (Abraham's bosom) or the darkness of Hades, following the Temporary Judgment. Orthodox do not accept the doctrine of Purgatory, which is held by Catholicism. The soul's experience of either of these states is only a "foretaste"—being experienced only by the soul—until the Final Judgment, when the soul and body will be reunited.^[111][112]

The Eastern Orthodox believe that the state of the soul in Hades can be affected by the love and prayers of the righteous up until the Last Judgment.^[113] For this reason the Church offers a special prayer for the dead on the third day, ninth day, fortieth day, and the one-year anniversary after the death of an Orthodox Christian. There are also several days throughout the year that are set aside for general commemoration of the departed, sometimes including nonbelievers. These days usually fall on a Saturday, since it was on a Saturday that Christ lay in the Tomb.^[112]

While the Eastern Orthodox consider the text of the Apocalypse (Book of Revelation) to be a part of Scripture, it is also regarded to be a holy mystery. Speculation on the contents of Revelation are minimal and it is never read as part of the regular order of services. Those theologians who have delved into its pages tend to be amillennialist in their eschatology, believing that the "thousand years" spoken of in biblical prophecy refers to the present time: from the Crucifixion of Christ until the Second Coming.

While it is not usually taught in church it is often used as a reminder of God's promise to those who love him, and of the benefits of avoiding sinful passions. Iconographic depictions of the Final Judgment are often portrayed on the back (western) wall of the church building to remind the departing faithful to be vigilant in their struggle against sin. Likewise it is often painted on the walls of the Trapeza (refectory) in a monastery where monks may be inspired to sobriety and detachment from worldly things while they eat.

The Eastern Orthodox believe that Hell, though often described in metaphor as punishment inflicted by God, is in reality the soul's rejection of God's infinite love which is offered freely and abundantly to everyone.

The Eastern Orthodox believe that after the Final Judgment:

The official Bible of the Eastern Orthodox Church contains the Septuagint text of the Old Testament, with the Book of Daniel given in the translation by Theodotion. The Patriarchal Text is used for the New Testament.^{[114][115][116]} Orthodox Christians hold that the Bible is a verbal icon of Christ, as proclaimed by the 7th ecumenical council.^[117] They refer to the Bible as Holy Scripture, meaning writings containing the foundational truths of the Christian faith as revealed by Christ and the Holy Spirit to its divinely inspired human authors. Holy Scripture forms the primary and authoritative written witness of Holy Tradition and is essential as the basis for all Orthodox teaching and belief.^[118] The Bible provides the only texts held to be suitable for reading in Orthodox worship services. Through the many scriptural quotations embedded in the worship service texts themselves, it is often said that the Eastern Orthodox pray the Bible as well as read it.

St. Jerome completed the well-known Vulgate Latin translation only in the early 5th century, around the time the accepted lists of scripture were resolved in the west. The east took up to a century longer to resolve the lists in use there, and ended by accepting a few additional writings from the Septuagint that did not appear in the lists of the west. The differences were small and were not considered to compromise the unity of the faith shared between east and west. They did not play a role in the eventual schism in the 11th century that separated the See of Rome and the West from the See of Constantinople and the other apostolic Orthodox churches, and remained as defined essentially without controversy in the East or West for at least one thousand years. It was only in the 16th century that Reformation Protestants challenged the lists, proclaiming a canon that rejected those Old Testament books that did not appear in the 3rd-century Hebrew Bible. In response, the Catholic and Eastern Orthodox churches reaffirmed their accepted scriptural lists in more formal canons of their own.

Once established as Holy Scripture, there has never been any question that the Eastern Orthodox Church holds the full list of books to be venerable and beneficial for reading and study,^[119] even though it informally holds some books in higher esteem than others, the four gospels highest of all. Of the subgroups significant enough to be named, the "Anagignoskomena" (ἀναγιγνωσκόμενα, "things that are read") comprises ten of the Old Testament books rejected in the Protestant canon,^[120] but deemed by the Eastern Orthodox worthy to be read in worship services, even though they carry a lesser esteem than the 39 books of the Hebrew canon.^[121] The lowest tier contains the remaining books not accepted by either Protestants or Catholics, among them, Psalm 151. Though it is a psalm, and is in the book of psalms, it is not classified as being within the Psalter (the first 150 psalms),^[122] and hence does not participate in the various liturgical and prayer uses of the Psalter.

In a very strict sense, it is not entirely orthodox to call the Holy Scriptures the "Word of God". That is a title the Eastern Orthodox Church reserves for Christ, as supported in the scriptures themselves, most explicitly in the first chapter of the gospel of John. God's Word is not hollow, like human words. "God said, 'let there be light'; and there was light."^[123] This is the Word which spoke the universe into being, and resonates in creation without diminution throughout all history, a Word of divine power.

As much as the Eastern Orthodox Church reveres and depends on the scriptures, they cannot compare to the Word of God's manifest action. But the Eastern Orthodox do believe that the Holy Scriptures testify to God's manifest actions in history, and that through its divine inspiration God's Word is manifested both in the scriptures themselves and in the cooperative human participation that composed them. It is in that sense that the Eastern Orthodox refer to the scriptures as "God's Word".

The Eastern Orthodox Church does not subscribe to the Protestant doctrine of sola scriptura. The church has defined what Scripture is; it also interprets what its meaning is.^[124] Christ promised: "When He, the Spirit of truth, has come, He will guide you into all truth".^[125] The Holy Spirit, then, is the infallible guide for the church to the interpretation of Scripture. The church depends upon those saints who, by lives lived in imitation of Christ, achieving theosis, can serve as reliable witnesses to the Holy Spirit's guidance. Individual interpretation occurs within the church and is informed by the church. It is rational and reasoned, but is not arrived at only by means of deductive reasoning.

Scriptures are understood to contain historical fact, poetry, idiom, metaphor, simile, moral fable, parable, prophecy and wisdom literature, and each bears its own consideration in its interpretation. While divinely inspired, the text stills consists of words in human languages, arranged in humanly recognizable forms. The Eastern Orthodox Church does not oppose honest critical and historical study of the Bible.^[126] In biblical interpretation, it does not use speculations, suggestive theories, or incomplete indications, not going beyond what is fully known.

"That faith which has been believed everywhere, always, and by all", the faith taught by Jesus to the apostles, given life by the Holy Spirit at Pentecost, and passed down to future generations without additions and without subtractions, is known as holy tradition.^[127][128] Holy tradition does not change in the Eastern Orthodox Church because it encompasses those things that do not change: the nature of the one God in Trinity, Father, Son, and Holy Spirit, the history of God's interactions with his peoples, the Law as given to the Israelites, all Christ's teaching as given to the disciples and Jews and recorded in scripture, including the parables, the prophecies, the miracles, and his own example to humanity in his extreme humility. It encompasses also the worship of the church, which grew out of the worship of the synagogue and temple and was extended by Christ at the last supper, and the relationship between God and his people which that worship expresses, which is also evidenced between Christ and his disciples. It includes the authority that Christ bestowed on his disciples when he made them apostles,^[129] for the preserving and teaching of the faith, and for governing the organization and conduct of the church (in its administration by bishops).

Holy tradition is firm, even unyielding, but not rigid or legalistic; instead, it lives and breathes within the church.^[130] For example, the New Testament was entirely written by the early church (mostly the apostles). The whole Bible was accepted as scripture by means of holy tradition practiced within the early church. The writing and acceptance took five centuries, by which time the Holy Scriptures themselves had become in their entirety a part of holy tradition.^[131] But holy tradition did not change, because "that faith which has been believed everywhere, always, and by all" remained consistent, without additions, and without subtractions. The historical development of the Divine Liturgy and other worship services and devotional practices of the church provide a similar example of extension and growth "without change".^[132]

The continuity and stability of Orthodox worship throughout the centuries is one means by which holy tradition expresses the unity of the whole church throughout time. Not only can the Eastern Orthodox of today visit a church in a place that speaks a language unknown to the visitors yet have the service remain familiar and understandable to them, but the same would hold true were any able to visit past eras. The church strives to preserve holy tradition "unchanging" that it may express the one unchanging faith for all time to come as well.

Besides these, holy tradition includes the doctrinal definitions and statements of faith of the seven ecumenical councils, including the Nicene-Constantinopolitan Creed, and some later local councils, patristic writings, canon law, and icons.^[126] Not all portions of holy tradition are held to be equally strong. Some, the Holy Scriptures foremost, certain aspects of worship, especially in the Divine Liturgy, the doctrines of the ecumenical councils, the Nicene-Constantinopolitan Creed, possess a verified authority that endures forever, irrevocably.^[126] However, with local councils and patristic writings, the church applies a selective judgement. Some councils and writers have occasionally fallen into error, and some contradict each other.^[126]

In other cases, opinions differ, no consensus is forthcoming, and all are free to choose. With agreement among the Church Fathers, though, the authority of interpretation grows, and full patristic consensus is very strong. With canon law (which tends to be highly rigorous and very strict, especially with clergy) an unalterable validity also does not apply, since canons deal with living on earth, where conditions are always changing and each case is subject to almost infinite variation from the next.^[126] Even when and where they were once used with full strictness, their application was not absolute, and was carried out for individuals under the pastoral care of their bishop, who had the authority to decide when individual discipline had been satisfied. This too is a part of the holy tradition.

By tradition, the Eastern Orthodox Church, when faced with issues that are larger than a single bishop can resolve, holds a local council. The bishops and such others as may attend convene (as St. Paul called the Corinthians to do) to seek the mind of the church.^[133] A council's declarations or edicts then reflect its consensus (if one can be found). An ecumencial council is only called for issues of such import or difficulty or pervasiveness that smaller councils are insufficient to address them. Ecumenical councils' declarations and canons carry binding weight by virtue of their representation across the whole church, by which the mind of the church can be readily seen. However, not all issues are so difficult as to require an ecumenical council to resolve. Some doctrines or decisions, not defined in a formal statement or proclaimed officially, nevertheless are held by the church unshakably and unanimously without internal disturbance, and these, also reflecting the mind of the church, are just as firmly irrevocable as a formal declaration of an ecumenical council. Lack of formality does not imply lack of authority within holy tradition.^[126] An example of such unanimity can be found in the acceptance in the 5th century of the lists of books that comprise Holy Scripture, a true canon without official stamp.

During the course of the early church, there were numerous followers who attached themselves to the Christ and his mission here on Earth, as well as followers who retained the distinct duty of being commissioned with preserving the quality of life and lessons revealed through the experience of Jesus living, dying, resurrecting and ascending among them. As a matter of practical distinction and logistics, people of varying gifts were accorded stations within the community structure— ranging from the host of agape meals (shared with brotherly and fatherly love), to prophecy and the reading of Scripture, to preaching and interpretations and giving aid to the sick and the poor. Sometime after Pentecost the Church grew to a point where it was no longer possible for the Apostles to minister alone. Overseers (bishops)^[134] and assistants (deacons and deaconesses)^[135] were appointed to further the mission of the Church.

The church recognised the gathering of these early church communities as being greatest in areas of the known world that were famous for their significance on the world stage—either as hotbeds of intellectual discourse, high volumes of trade, or proximity to the original sacred sites. These locations were targeted by the early apostles, who recognised the need for humanitarian efforts in these large urban centers and sought to bring as many people as possible into the church—such a life was seen as a form of deliverance from the decadent lifestyles promoted throughout the eastern and western Roman empires.

As the church increased in size through the centuries, the logistic dynamics of operating such large entities shifted: patriarchs, metropolitans, archimandrites, abbots and abbesses, all rose up to cover certain points of administration.^[136]

As a result of heightened exposure and popularity of the philosophical schools (haereseis) of Greco-Roman society and education, synods and councils were forced to engage such schools that sought to co-opt the language and pretext of the Christian faith in order to gain power and popularity for their own political and cultural expansion. As a result, ecumenical councils were held to attempt to rebuild solidarity by using the strength of distant orthodox witnesses to dampen the intense local effects of particular philosophical schools within a given area.

While originally intended to serve as an internal check and balance for the defense of the doctrine developed and spread by the apostles to the various sees against faulty local doctrine, at times the church found its own bishops and emperors falling prey to local conventions. At these crucial moments in the history of the church, it found itself able to rebuild on the basis of the faith as it was kept and maintained by monastic communities, who subsisted without reliance on the community of the state or popular culture and were generally unaffected by the materialism and rhetoric that often dominated and threatened the integrity and stability of the urban churches.

In this sense, the aim of the councils was not to expand or fuel a popular need for a clearer or relevant picture of the original apostolic teaching. Rather, the theologians spoke to address the issues of external schools of thought who wished to distort the simplicity and neutrality of the apostolic teaching for personal or political gain. The consistency of the Eastern Orthodox faith is entirely dependent on the Holy Tradition of the accepted corpus of belief–the decisions ratified by the fathers of the seven ecumenical councils, and this is only done at the beginning of a consecutive council so that the effects of the decisions of the prior council can be audited and verified as being both conceptually sound and pragmatically feasible and beneficial for the church as a whole.

The minority of autocephalous Orthodox churches, but the majority of the members of the Eastern Orthodox Church, follow the Julian calendar. The majority of Orthodox autocephalous churches follow the Revised Julian calendar. The autonomous Church of Finland of the Ecumenical Patriarchate, as well as parts of the Church of the Czech Lands and Slovakia, use the Gregorian calendar. Many church traditions, including the schedules of services, feasts, and fasts, are structured by the church's calendar, which provides a strictly observed intermingled set of cycles of varying lengths. The fixed annual cycle begins on 1 September and establishes the times for all annual observances that are fixed by date, such as Christmas. The annual Paschal cycle is established relative to the varying date of Pascha each year and affects the times for such observances as Pascha itself, Great Lent, Holy Week, and the feasts of Ascension and Pentecost.

Lesser cycles also run in tandem with the annual ones. A weekly cycle of days prescribes a specific focus for each day in addition to others that may be observed.^[137]

The services of the church are conducted each day according to the church calendar. Parts of each service remain fixed, while others change depending on the observances prescribed for the specific day in the various cycles, ever providing a flow of constancy within variation. Services are conducted in the church and involve both the clergy and faithful. Services cannot properly be conducted by a single person, but must have at least one other person present (i.e. a priest cannot celebrate alone, but must have at least a chanter present and participating).

Usually, all of the services are conducted on a daily basis only in monasteries and cathedrals, while parish churches might only do the services on the weekend and major feast days. On certain Great Feasts (and, according to some traditions, every Sunday) a special All-Night Vigil (Agrypnia) will be celebrated from late at night on the eve of the feast until early the next morning. Because of its festal nature it is usually followed by a breakfast feast shared together by the congregation.

Services, especially the Divine Liturgy, may only be celebrated once a day on a single altar (some churches have multiple altars in order to accommodate large congregations). Each priest may only celebrate the Divine Liturgy once a day.

From its Jewish roots, the liturgical day begins at sundown. The traditional daily cycle of services is as follows:

The Divine Liturgy is the celebration of the Eucharist. Although it is usually celebrated between the Sixth and Ninth Hours, it is not considered to be part of the daily cycle of services, as it occurs outside the normal time of the world. The Divine Liturgy is not celebrated on weekdays during Great Lent, and in some places during the lesser fasting seasons either; however, reserve communion is prepared on Sundays and is distributed during the week at the Liturgy of the Presanctified Gifts.

Other items brought to the altar during the Divine Liturgy include a gold or silver chalice with red wine, a small metallic urn of warm water, a metallic communion spoon, a little metallic spear, a sponge, a metal disk with cut pieces of bread upon it, and a star, which is a star-shaped piece of metal over which the priest places a cloth covering when transporting the holy gifts to and from the altar. Also found on the altar table is the antimins. The antimins is a silk cloth, signed by the appropriate diocesan bishop, upon which the sanctification of the holy gifts takes place during each Divine Liturgy. The antimins contain the relics of a saint. When a church is consecrated by a bishop, there is a formal service or prayers and sanctification in the name of the saint that the church is named after. The bishop will also often present a small relic of a saint to place in or on the altar as part of the consecration of a new church.

The book containing liturgically read portions of the four gospels is permanently "enthroned" on the altar table. Eastern Orthodox bishops, priests, deacons and readers sing/chant specific verses from this Gospel Book on each different day of the year.

This daily cycle services is conceived of as both the sanctification of time (chronos, the specific times during which they are celebrated), and entry into eternity (kairos). They consist to a large degree of litanies asking for God's mercy on the living and the dead, readings from the Psalter with introductory prayers, troparia, and other prayers and hymns surrounding them. The Psalms are so arranged that when all the services are celebrated the entire Psalter is read through in their course once a week, and twice a week during Great Lent when the services are celebrated in an extended form.

Orthodox services are sung nearly in their entirety. Services consist in part of a dialogue between the clergy and the people (often represented by the choir or the Psaltis Cantor). In each case the prayers are sung or chanted following a prescribed musical form. Almost nothing is read in a normal speaking voice, with the exception of the homily if one is given.

Because the human voice is seen as the most perfect instrument of praise, musical instruments (organs, etc.) are not generally used to accompany the choir.

The church has developed eight modes or tones (see Octoechos) within which a chant may be set, depending on the time of year, feast day, or other considerations of the Typikon. There are numerous versions and styles that are traditional and acceptable and these vary a great deal between cultures.^[138] It is common, especially in the United States, for a choir to learn many different styles and to mix them, singing one response in Greek, then English, then Russian, etc.

In the Russian tradition there have been some famous composers of "unaccompanied" church music, such as Tchaikovsky (Liturgy of St John Chrysostom, op. 41, 1878, and All-Night Vigil, op. 52, 1882) and Rachmaninoff (Liturgy of St John Chrysostom, op. 31, 1910, and All-Night Vigil, op. 37, 1915); and many church tones can likewise be heard influencing their music.

As part of the legacy handed down from its Judaic roots, incense is used during all services in the Eastern Orthodox Church as an offering of worship to God as it was done in the Jewish First and Second Temples in Jerusalem (Exodus chapter 30). Incense is also prophesied in the book of Malachi 1:11 as a "pure offering" in the glorification of God by the Gentiles in "every place" where the name of God is regarded as "great". Traditionally, the base of the incense used is the resin of Boswellia sacra, also known as frankincense, but the resin of fir trees has been used as well. It is usually mixed with various floral essential oils giving it a sweet smell.

Incense represents the sweetness of the prayers of the saints rising up to God (Psalm 141:2, Revelation 5:8, 8:4). The incense is burned in an ornate golden censer that hangs at the end of three chains representing the Trinity. Two chains represent the human and Godly nature of the Son, one chain for the Father and one chain for the Holy Spirit. The lower cup represents the earth and the upper cup the heaven. In the Greek, Slavic, and Syrian traditions there are 12 bells hung along these chains representing the 12 apostles. There are also 72 links representing 72 evangelists.

The charcoal represents the sinners. Fire signifies the Holy Spirit and frankincense the good deeds. The incense also represents the grace of the Trinity. The censer is used (swung back and forth) by the priest/deacon to venerate all four sides of the altar, the holy gifts, the clergy, the icons, the congregation, and the church structure itself. Incense is also used in the home where the individual will go around the house and "cross" all of the icons saying in Greek: Ἅγιος ὁ Θεός, Ἅγιος ἰσχυρός, Ἅγιος ἀθάνατος, ἐλέησον ἡμᾶς, or in English: Holy God, Holy Mighty, Holy Immortal, have mercy on us.

The number of fast days varies from year to year, but in general the Eastern Orthodox Christian can expect to spend a little over half the year fasting at some level of strictness. There are spiritual, symbolic, and even practical reasons for fasting. In the Fall from Paradise mankind became possessed by a carnal nature; that is to say, became inclined towards the passions. Through fasting, Orthodox Christians attempt to return to the relationship of love and obedience to God enjoyed by Adam and Eve in Paradise in their own lives, by refraining from carnal practices, by bridling the tongue (James 3:5–6), confession of sins, prayer and almsgiving.

Fasting is seen as purification and the regaining of innocence. It is a practice of learning to temper the body's primary desire for food. By learning to temper this basic desire of the body, the practitioner can more readily temper other worldly desires, and thus, become better enabled to draw closer to God in the hope of becoming more Christ-like. Through obedience to the church and its ascetic practices the Eastern Orthodox Christian seeks to rid himself or herself of the passions (The desires of our fallen carnal nature). All Orthodox Christians are provided with a prescribed set of guidelines. They do not view fasting as a hardship, but rather as a privilege and joy. The teaching of the Church provides both the time and the amount of fasting that is expected as a minimum for every member who chooses to participate. For greater ascesis, some may choose to go without food entirely for a short period of time. A complete three-day fast at the beginning and end of a fasting period is not unusual, and some fast for even longer periods, though this is usually practiced only in monasteries.

In general, fasting means abstaining from meat and meat products, dairy (eggs and cheese) and dairy products, fish, olive oil, and wine. Wine and oil—and, less frequently, fish—are allowed on certain feast days when they happen to fall on a day of fasting; but animal products and dairy are forbidden on fast days, with the exception of "Cheese Fare" week which precedes Great Lent, during which dairy products are allowed. Wine and oil are usually also allowed on Saturdays and Sundays during periods of fast. In some Orthodox traditions, caviar is permitted on Lazarus Saturday, the Saturday before Palm Sunday, although the day is otherwise a fast day. Married couples also abstain from sexual activity on fast days so that they may devote themselves fulsomely to prayer (1 Corinthians 7:5).

While it may seem that fasting in the manner set forth by the Church is a strict rule, there are circumstances where a person's spiritual guide may allow an Economy because of some physical necessity (e.g. those who are pregnant or infirm, the very young and the elderly, or those who have no control over their diet, such as prisoners or soldiers).

The time and type of fast is generally uniform for all Orthodox Christians; the times of fasting are part of the ecclesiastical calendar, and the method of fasting is set by canon law and holy tradition. There are four major fasting periods during the year: Nativity Fast, Great Lent, Apostles' Fast, and the Dormition Fast. In addition to these fasting seasons, Orthodox Christians fast on every Wednesday (in commemoration of Christ's betrayal by Judas Iscariot), and Friday (in commemoration of Christ's Crucifixion) throughout the year. Monastics often fast on Mondays.

Orthodox Christians who are preparing to receive the Eucharist do not eat or drink at all from vespers (sunset) until after taking Holy Communion. A similar total fast is expected to be kept on the Eve of Nativity, the Eve of Theophany (Epiphany), Great Friday and Holy Saturday for those who can do so. There are other individual days observed as fasts (though not as days of total fasting) no matter what day of the week they fall on, such as the Beheading of St. John the Baptist on 29 August and the Exaltation of the Holy Cross on 14 September.

Almsgiving, more comprehensively described as "acts of mercy", refers to any giving of oneself in charity to someone who has a need, such as material resources, work, assistance, counsel, support, or kindness. Along with prayer and fasting, it is considered a pillar of the personal spiritual practices of the Eastern Orthodox Christian tradition. Almsgiving is particularly important during periods of fasting, when the Eastern Orthodox believer is expected to share with those in need the monetary savings from his or her decreased consumption. As with fasting, mentioning to others one's own virtuous deeds tends to reflect a sinful pride, and may also be considered extremely rude.

The Eastern Orthodox Church places heavy emphasis and awards a high level of prestige to traditions of monasticism and asceticism with roots in Early Christianity in the Near East and Byzantine Anatolia. The most important centres of Christian Orthodox monasticism are Saint Catherine's Monastery in the Sinai Peninsula (Egypt) and Mount Athos in Northern Greece.

All Orthodox Christians are expected to participate in at least some ascetic works, in response to the commandment of Christ to "come, take up the cross, and follow me." (Mark 10:21 and elsewhere) They are therefore all called to imitate, in one way or another, Christ himself who denied himself to the extent of literally taking up the cross on the way to his voluntary self-sacrifice. However, laypeople are not expected to live in extreme asceticism since this is close to impossible while undertaking the normal responsibilities of worldly life.

Those who wish to do this therefore separate themselves from the world and live as monastics: monks and nuns. As ascetics par excellence, using the allegorical weapons of prayer and fasting in spiritual warfare against their passions, monastics hold a very special and important place in the Church. This kind of life is often seen as incompatible with any kind of worldly activity including that which is normally regarded as virtuous. Social work, school teaching, and other such work is therefore usually left to laypeople. Ascetics of the Eastern Orthodox Church are recognised by their long hair, and in case of male monks, long beards.

There are three main types of monastics. Those who live in monasteries under a common rule are coenobitic. Each monastery may formulate its own rule, and although there are no religious orders in Orthodoxy some respected monastic centers such as Mount Athos are highly influential. Eremitic monks, or hermits, are those who live solitary lives. It is the yearning of many who enter the monastic life to eventually become solitary hermits. This most austere life is only granted to the most advanced monastics and only when their superiors feel they are ready for it.

Hermits are usually associated with a larger monastery but live in seclusion some distance from the main compound. Their local monastery will see to their physical needs, supplying them with simple foods while disturbing them as little as possible. In between are those in semi-eremitic communities, or sketes, where one or two monks share each of a group of nearby dwellings under their own rules and only gather together in the central chapel, or katholikon, for liturgical observances.

The spiritual insight gained from their ascetic struggles make monastics preferred for missionary activity. Bishops are almost always chosen from among monks, and those who are not generally receive the monastic tonsure before their consecrations.

Many (but not all) Orthodox seminaries are attached to monasteries, combining academic preparation for ordination with participation in the community's life of prayer. Monks who have been ordained to the priesthood are called hieromonk (priest-monk); monks who have been ordained to the diaconate are called hierodeacon (deacon-monk). Not all monks live in monasteries, some hieromonks serve as priests in parish churches thus practicing "monasticism in the world".

Cultural practices differ slightly, but in general Father is the correct form of address for monks who have been tonsured, while Novices are addressed as Brother. Similarly, Mother is the correct form of address for nuns who have been tonsured, while Novices are addressed as Sister. Nuns live identical ascetic lives to their male counterparts and are therefore also called monachoi (monastics) or the feminine plural form in Greek, monachai, and their common living space is called a monastery.

Everything in the Eastern Orthodox Church has a purpose and a meaning revealing God's revelation to man. At the front, or eastern end of the church, is a raised dais with an icon-covered screen or wall (iconostasis or templon) separating the nave from the sanctuary. In the center of this wall is the entrance to the altar known as the "Royal Doors" through which only the clergy may pass.

There is a right and left side door on the front of the iconostasis, one depicting the archangel, Michael and the other Gabriel. The priest and altar boys enter and exit through these doors during appropriate parts of the Divine Liturgy. Immediately to the right of the main gate you will always find an icon of Jesus Christ, on the left, an icon of the Theotokos (Mother of God). Other icons depicted on the iconostasis are Saint John the Forerunner and the Saint after which the church is named.

In front of the iconostasis is the bishop's chair, a place of honor where a visiting bishop or metropolitan will often sit when visiting the church. An Orthodox priest, when standing at the altar during the Divine Liturgy, faces toward the altar (typically facing east) and properly leads his congregation while together they perform the mystical sacrifice and pray to God.

The sanctuary contains the Holy Altar, representing the place where Orthodox Christians believe that Christ was born of the virgin Mary, crucified under Pontius Pilate, laid in the tomb, descended into hell, rose from the dead on the third day, ascended into heaven, and will return again at his second coming. A free-standing cross, bearing the body of Christ, may stand behind the altar. On the altar are a cloth covering, a large book containing the gospel readings performed during services, an ark containing presanctified divine gifts (bread and wine) distributed by the deacon or priest to those who cannot come to the church to receive them, and several white beeswax candles.

The term 'icon' comes from the Greek word eikon, which simply means image. The Eastern Orthodox believe that the first icons of Christ and the Virgin Mary were painted by Luke the Evangelist. Icons are filled with symbolism designed to convey information about the person or event depicted. For this reason, icons tend to be formulaic, following a prescribed methodology for how a particular person should be depicted, including hair style, body position, clothing, and background details.

Icon painting, in general, is not an opportunity for artistic expression, though each iconographer brings a vision to the piece. It is far more common for an icon to be copied from an older model, though with the recognition of a new saint in the church, a new icon must be created and approved. The personal and creative traditions of Catholic religious art were largely lacking in Orthodox icon painting before the 17th century, when Russian icons began to be strongly influenced by religious paintings and engravings from both Protestant and Catholic Europe. Greek icons also began to take on a strong western influence for a period and the difference between some Orthodox icons and western religious art began to vanish. More recently there has been a trend of returning to the more traditional and symbolic representations.

Aspects of the iconography borrow from the pre-Christian Roman and Hellenistic art. Henry Chadwick wrote, "In this instinct there was a measure of truth. The representations of Christ as the Almighty Lord on his judgment throne owed something to pictures of Zeus. Portraits of the Mother of God were not wholly independent of a pagan past of venerated mother-goddesses. In the popular mind the saints had come to fill a role that had been played by heroes and deities."^[139]

Large free-standing statues (three-dimensional depictions) are almost non-existent in the Eastern Orthodox Church. This is partly because cult images of the Greek gods were a focus of the ancient Greek religion and its Roman equivalent, and much criticised by Early Christian writers, and partly because icons are meant to show the spiritual nature of man, not the sensual earthly body. Reliefs, however, were used in Byzantine art.

Icons are not considered by the Eastern Orthodox to be idols or objects of worship. The parameters of their usage were clearly spelled out by the 7th ecumenical council. Justification for their usage utilises the following logic: before God took human form in Christ, no material depiction was possible and therefore blasphemous even to contemplate. Once God became incarnate, depiction was possible.

As Christ is believed to be God, it is justified to hold in one's mind the image of God-incarnate. Likewise, when one venerates an icon, it is not the wood or paint that are venerated but rather the individual shown, just as it is not the paper one loves when one might kiss the photograph of a loved one. As Saint Basil famously proclaimed, honour or veneration of the icon always passes to its archetype. Following this reasoning, the veneration of the glorified human saint made in God's image, is always a veneration of the divine image, and hence God as foundational archetype.

Icons can be found adorning the walls of churches and often cover the inside structure completely.^[140] Most Orthodox homes have an area set aside for family prayer, usually an eastern facing wall, where are hung many icons. Icons have been part of Orthodox Christianity since the beginning of the church.^[141]

Icons are often illuminated by a candle or oil lamp (beeswax for candles and olive oil for lamps are preferred because they are natural and burn cleanly). Besides the practical purpose of making icons visible in an otherwise dark church, both candles and oil lamps symbolise the Light of the World, who is Christ.

Tales of miraculous icons are not uncommon, though it has always been considered that the message of such an event was for the immediate faithful involved and therefore does not usually attract crowds. Some miraculous icons whose reputations span long periods of time nevertheless become objects of pilgrimage along with the places where they are kept. As several Orthodox theologians and saints have explored in the past, the icon's miraculous nature is found not in the material, but in the glory of the saint who is depicted. The icon is a window, in the words of Paul Florensky, that actually participates in the glory of what it represents.

An iconostasis, also called the templon, is a wall of icons and religious paintings, separating the nave from the sanctuary in a church. Iconostasis also refers to a portable icon stand that can be placed anywhere within a church. The modern iconostasis evolved from the Byzantine templon in the 11th century. The evolution of the iconostasis probably owes a great deal to 14th-century Hesychast mysticism and the wood-carving genius of the Russian Orthodox Church.

The first ceiling-high, five-leveled Russian iconostasis was designed by Andrey Rublyov in the cathedral of the Dormition in Vladimir in 1408. The separation between sanctuary and nave accomplished by the iconostasis is not mandatory, though it is common practice. Depending on circumstance, the role of the iconostasis can be played by masonry, carved panels, screens, curtains, railings, a cord or rope, plain icons on stands, steps, or nothing at all.

Depictions of the cross within the Eastern Orthodox Church are numerous and often highly ornamented, but its use does not extend to all Orthodox traditions. Some carry special significance. The Tri-Bar Cross, popular in Russia, Ukraine, and Belarus, but common throughout the Eastern Orthodox world, seen to the left, has three bars. Its origins are in the early Byzantine Church of the 4th century AD.

The small top crossbar represents the sign that Pontius Pilate nailed above Christ's head. It often is inscribed with an acronym, "INRI", Latin, meaning "Jesus of Nazareth, King of the Jews" or "INBI", Greek, "Jesus of Nazareth, King of the Jews"; however, it is often replaced or amplified by the phrase "The King of Glory" in order to answer Pilate's statement with Christ's affirmation, "My Kingdom is not of this world".

There is also a bottom slanting bar which has several explanations. Claims of evidence indicate that there was a small wooden platform for the crucified to stand on in order to support his weight; in Jesus' case his feet were nailed side by side to this platform with one nail each in order to prolong the torture of the cross.

Implied evidence for this comes mainly from two sources, namely, the Bible (in order to cause the victim to die faster, his legs were broken so they could not support his weight and he would suffocate) and iconography (all early depictions of the crucifixion show this arrangement, not the later with feet on top with single nail). It has also been pointed out by some experts that the nailed hands of a body crucified in the manner often shown in modern secular art would not support the weight of the body and would tear through. A platform for the feet would relieve this problem.

That the bottom bar is slanted has two explanations, to represent the very real agony which Christ experienced on the cross (a refutation of Docetism) and to signify that the thief on Christ's right chose the right path while the thief on the left did not.

Other crosses associated with the Eastern Orthodox Church are the more traditional single-bar crosses, budded designs, the Greek cross, the Latin cross, the Jerusalem cross (cross pattée), Celtic crosses, and others.^[142] A common symbolism of the slanted foot stool is The foot-rest points up, toward Heaven, on Christ's right hand-side, and downward, to Hades, on Christ's left. "Between two thieves Thy Cross did prove to be a balance of righteousness: wherefore one of them was dragged down to Hades by the weight of his blasphemy [the balance points downward], whereas the other was lightened of his transgressions unto the comprehension of theology [the balance points upward]. O Christ God, glory to Thee."^[143] Another Orthodox cross which is worn in gold is an outer budded cross with an inner Three Bar Cross. The inscription Jesus Christ in Greek: IC (Iesous) on the left side bar and XC (Xhristos) on the right side bar, with a sun on the top of the cross. There is also typically an inscription on the back in Church Slavonic: "спаси и сохрани", "Spasi i Sokhrani", "Save and Protect". This cross is known as the Saint Olga Cross.^[144]

The church building has many symbolic meanings; perhaps the oldest and most prominent is the concept that the church is the Ark (as in Noah's) in which the world is saved from the flood of temptations; therefore, most Orthodox churches are rectangular in design. Another popular configuration, especially for churches with large choirs is cruciform or cross-shaped or what is called the "Greek-cross."

Architectural patterns vary in shape and complexity, with chapels sometimes added around the main church, or triple altars; but in general, the symbolic layout of the church remains the same. Each church is created with specified qualifications based on what the apostles said in the Bible. These qualifications include how big the temple should be.

The church building is divided into three main parts: the narthex (vestibule), the nave and the sanctuary (also called the altar or holy place). The narthex is where catechumens and non-Orthodox visitors were traditionally asked to stand during services. It is separated from the nave by "The Royal Gate". On each side of this gate are candle stands (menalia) representing the pillars of fire that went before the Hebrew people escaping from Egypt.

The nave is where most of the congregation stand during services. Traditionally, men stand on the right and women on the left. This is for a number of reasons: (1) Considering the family unit of past centuries the husband was dominant; thus, standing the same distance from the altar, equality is emphasised. (2) The idea of separating the sexes was inherited from the Jewish tradition of doing so within synagogues (3) Separation of sexes also followed the practice of choirs in which different levels of voice are placed in groups to facilitate harmony.

In general, men and women dress respectfully, typically wearing their "Sunday best" to enter the church. Often, women cover their heads as prescribed by Paul (1 Cor. 11:13). Children are considered full members of the church and stand attentively and quietly during services. There is often a choir area at the side or in a loft in back. In addition to the choir, a chanter is always present at the front of the church to chant responses and hymns that are part of the Divine Liturgy offered by the priest. There is usually a dome in the ceiling with an icon of Christ depicted as Ruler of the Universe (Pantocrator).

The Archdiocesan Cathedral of the Holy Trinity on New York City's Upper East Side is the largest Orthodox Christian church in the Western Hemisphere.^[145]

Apart from the icons, the Eastern Orthodox churches and monasteries are often decorated with frescos and mosaics.

The Eastern Orthodox Church also has many associated traditions (sometimes referred to simply as customs), compatible with its life and function, but not necessarily tied so closely to the faith itself. These are not generally regarded as a part of Holy Tradition, though no strict dividing line is drawn. As long as compatibility is maintained, general practice often tends to the permissive rather than the restrictive, with the local priest or bishop resolving questions.

Many of these customs are local or cultural, and some are not even especially religious, but form a part of the church's relationship with the people in the time and place where it exists. Where outside customs affect church practices such as worship, a closer watch is kept for guarding the integrity of worship, but suitable local differences are welcomed and celebrated joyfully. The local church customs, especially liturgical ones, are referred to as differences in typica (Style).

Locality is also expressed in regional terms of churchly jurisdiction, which is often also drawn along national lines. Many Orthodox churches adopt a national title (e.g. Albanian Orthodox, Bulgarian Orthodox, Antiochian Orthodox, Georgian Orthodox, Greek Orthodox, Montenegrin Orthodox, Romanian Orthodox, Russian Orthodox, Serbian Orthodox, Ukrainian Orthodox, etc.) and this title can identify which language is used in services, which bishops preside, and which of the typica is followed by specific congregations. In the Middle East, Orthodox Christians are usually referred to as Rum ("Roman") Orthodox, because of their historical connection with the Eastern Roman (Byzantine) Empire.^[146]

Differences in praxis ("practice") tend to be slight, involving things such as the order in which a particular set of hymns are sung or what time a particular service is celebrated. But observances of the saints' days of local saints are more often celebrated in special services within a locality, as are certain national holidays, like Greek Independence Day. In North America, observances of Thanksgiving Day are increasing.

Members of the church are fully united in faith and the sacred mysteries with all Orthodox congregations, regardless of nationality or location. In general, Orthodox Christians could travel the globe and feel familiar with the services even if they did not know the language being used.

In the Levant, Christian Orthodox services and identity often combine both the Byzantine Greek and indigenous (Arabic and Aramaic) traditions. Other Orthodox communities can identify with two Eastern Orthodox churches simultaneously, for example Caucasus Greeks and Pontic Greeks in Russia often identify with both the Greek Orthodox Church and Russian Orthodox Church, as a result of centuries of assimilation and intermarriage with ethnic Russians and other Christian Orthodox communities in mainly southern Russia.

According to Orthodox theology, the purpose of the Christian life is to attain theosis, the mystical union of mankind with God. This union is understood as both collective and individual. St. Athanasius of Alexandria wrote concerning the Incarnation that, "He (Jesus) was made man that we might be made god (θεοποιηθῶμεν)."^[147] See 2 Peter 1:4, John 10:34–36, Psalm 82:6. The entire life of the church is oriented towards making this possible and facilitating it.

In the Eastern Orthodox Church the terms "mystery" or "the mysteries" refer to the process of theosis. While it is understood that God theoretically can do anything instantly and invisibly, it is also understood that he generally chooses to use material substance as a medium in order to reach people. The limitations are those of mankind, not God. Matter is not considered to be evil by the Eastern Orthodox. Water, oil, bread, wine, etc., all are means by which God reaches out to allow people to draw closer to him. How this process works is a "mystery" and cannot be defined in human terms. These mysteries are surrounded by prayer and symbolism so that their true meaning will not be forgotten.

Those things which in the West are often termed sacraments or sacramentals are known among the Eastern Orthodox as the "sacred mysteries". While the Roman Catholic Church numbers seven sacraments, and many Protestant groups list two (baptism and the Eucharist) or even none, the Eastern Orthodox do not limit the number. However, for the sake of convenience, catechisms will often speak of the seven great mysteries. Among these are Holy Communion (the most direct connection), baptism, Chrismation, confession, unction, matrimony, and ordination. But the term also properly applies to other sacred actions such as monastic tonsure or the blessing of holy water, and involves fasting, almsgiving, or an act as simple as lighting a candle, burning incense, praying or asking God's blessing on food.^[148]

Baptism is the mystery which transforms the old and sinful person into a new and pure one; the old life, the sins, any mistakes made are gone and a clean slate is given. Through baptism a person is united to the Body of Christ by becoming a member of the Orthodox Church. During the service, water is blessed. The catechumen is fully immersed in the water three times in the name of the Trinity. This is considered to be a death of the "old man" by participation in the crucifixion and burial of Christ, and a rebirth into new life in Christ by participation in his resurrection.^[149] Properly a new name is given, which becomes the person's name.

Children of Orthodox families are normally baptised shortly after birth. Converts to Orthodoxy are usually formally baptised into the Orthodox Church, though exceptions are sometimes made. Those who have left Orthodoxy and adopted a new religion, if they return to their Orthodox roots, are usually received back into the church through the mystery of Chrismation.

Properly, the mystery of baptism is administered by bishops and priests; however, in emergencies any Orthodox Christian can baptise.^[150] In such cases, should the person survive the emergency, it is likely that the person will be properly baptised by a priest at some later date. This is not considered to be a second baptism, nor is it imagined that the person is not already Orthodox, but rather it is a fulfillment of the proper form.

The service of Baptism used in Orthodox churches has remained largely unchanged for over 1500 years. This fact is witnessed to by St. Cyril of Jerusalem (d. 386), who, in his Discourse on the Sacrament of Baptism, describes the service in much the same way as is currently in use.

Chrismation (sometimes called confirmation) is the mystery by which a baptised person is granted the gift of the Holy Spirit through anointing with Holy Chrism.^[151][152] It is normally given immediately after baptism as part of the same service, but is also used to receive lapsed members of the Orthodox Church.^[153] As baptism is a person's participation in the death and resurrection of Christ, so Chrismation is a person's participation in the coming of the Holy Spirit at Pentecost.^[154]

A baptised and chrismated Orthodox Christian is a full member of the church and may receive the Eucharist regardless of age.^[154]

The creation of Chrism may be accomplished by any bishop at any time, but usually is done only once a year, often when a synod of bishops convenes for its annual meeting. (Some autocephalous churches get their chrism from others.) Anointing with it substitutes for the laying-on of hands described in the New Testament, even when an instrument such as a brush is used.^[155]

The Eucharist is at the center of Orthodox Christianity. In practice, it is the partaking of the body and blood of Jesus Christ in the midst of the Divine Liturgy with the rest of the church. The bread and wine are believed to become the genuine body and blood of the Christ Jesus through the operation of the Holy Spirit. The Orthodox Church has never described exactly how this occurs, or gone into the detail that the Catholic Church has in the West.

Communion is given only to baptised and chrismated Orthodox Christians who have prepared by fasting, prayer and confession. The priest will administer the gifts with a spoon, called a "cochlear", directly into the recipient's mouth from the chalice.^[156] From baptism young infants and children are carried to the chalice to receive holy communion.^[154]

Because of the Orthodox understanding of mankind's fallen nature in general those who wish to commune prepare themselves in a way that reflects mankind in paradise. First, they prepare by having their confession heard and the prayer of repentance read over them by a priest. They will increase their prayer rule, adding the prescribed prayers in preparation for communing. Finally, they will fast completely from food and drink from the evening of the previous day (usually sunset on Saturday if communing on Sunday).

Orthodox Christians who have committed sins but repent of them, and who wish to reconcile themselves to God and renew the purity of their original baptisms, confess their sins to God before a spiritual guide who offers advice and direction to assist the individual in overcoming their sin. Parish priests commonly function as spiritual guides, but such guides can be any person, male or female (not commonly a layperson but in these cases monks or nuns), who has been given a blessing to hear confessions. Spiritual guides are chosen very carefully as this is a mandate that once chosen must be obeyed. Having confessed, the penitent then has his or her parish priest read the prayer of absolution over them.

Sin is not viewed by the Orthodox as a stain on the soul that needs to be wiped out, or a legal transgression that must be set right by a punitive sentence, but rather as a mistake made by the individual with the opportunity for spiritual growth and development. An act of penance (epitemia), if the spiritual guide requires it, is never formulaic, but rather is directed toward the individual and their particular problem, as a means of establishing a deeper understanding of the mistake made, and how to effect its cure. Because full participatory membership is granted to infants, it is not unusual for even small children to confess; though the scope of their culpability is far less than an older child, still their opportunity for spiritual growth remains the same.

From the Orthodox perspective, marriage is one of the holy mysteries or sacraments. As well as in many other Christian traditions, for example in Catholicism, it serves to unite a woman and a man in eternal union and love before God, with the purpose of following Christ and his Gospel and raising up a faithful, holy family through their holy union.^[157][158] The church understands marriage to be the union of one man and one woman, and certain Orthodox leaders have spoken out strongly in opposition to the civil institution of same-sex marriage.^[159][160]

Jesus said that "when they rise from the dead, they neither marry nor are given in marriage, but are like angels in heaven" (Mk 12:25). For the Orthodox Christian this passage should not be understood to imply that Christian marriage will not remain a reality in the Kingdom, but points to the fact that relations will not be "fleshy", but "spiritual".^[161] Love between wife and husband, as an icon of relationship between Christ and Church, is eternal.^[161]

The church does recognise that there are rare occasions when it is better that couples do separate, but there is no official recognition of civil divorces. For the Orthodox, to say that marriage is indissoluble means that it should not be broken, the violation of such a union, perceived as holy, being an offense resulting from either adultery or the prolonged absence of one of the partners. Thus, permitting remarriage is an act of compassion of the church towards sinful man.^[162] Ecclesiastically divorced Orthodox (not civilly divorced only) are usually allowed to remarry in the Orthodox Church, though there is usually imposed on them a fairly severe penance by their bishop and the services for a second marriage in this case are more penitential than joyful. Widows are permitted to remarry without repercussion and their second marriage is considered just as valid as the first. One exception to this rule is the clergy and their wives. Should a married priest die, it is normal that his wife will retire to a monastery once their children are out of the house. Widowed priests are not allowed to remarry (no priest may be married after his ordination) and also frequently end up in monasteries.

The service of marriage in the Orthodox Church has two distinct parts: the betrothal (engagement) and the crowning. There is no exchange of vows. There is a set expectation of the obligations incumbent on a married couple, and whatever promises they may have privately to each other are their responsibility to keep.

Since its founding, the church spread to different places and its leaders in each region came to be known as episkopoi (overseers, plural of episkopos, overseer—Gr. ἐπίσκοπος), which became "bishop" in English. The other ordained roles are presbyter (Gr. πρεσβύτερος, elder), which became "prester" and then "priest" in English, and diakonos (Gr. διάκονος, servant), which became "deacon" in English (see also subdeacon). There are numerous administrative positions among the clergy that carry additional titles.

In the Greek tradition, bishops who occupy an ancient see are called metropolitans, while the lead bishop in Greece is the archbishop. (In the Russian tradition, however, the usage of the terms "metropolitan" and "archbishop" is reversed.) Priests can be archpriests, archimandrites or protopresbyters. Deacons can also be archdeacons or protodeacons. The position of deacon is often occupied for life. The deacon also acts as an assistant to a bishop.

With the exception of bishops, who remain celibate, the Orthodox Church has always allowed priests and deacons to be married, provided the marriage takes place before ordination. In general it is considered preferable for parish priests to be married as they often act as counsel to married couples and thus can draw on their own experience. Unmarried priests usually are monks and live in monasteries, though there are occasions when, because of a lack of married priests, a monk-priest is temporarily assigned to a parish.

Widowed priests and deacons may not remarry and it is common for such members of the clergy to retire to a monastery (see clerical celibacy). This is also true of widowed wives of clergy, who do not remarry and become nuns when their children are grown. Only men are allowed to take holy orders, although deaconesses had both liturgical and pastoral functions within the church.^[163] However, it has fallen out of practice (the last deaconess was ordained in the 19th century).

In 2017, Patriarch Theodoros II and the Holy Synod of the Patriarchate of Alexandria decided to reinstate the order of deaconesses in the Greek Orthodox Church. In February, he appointed six nuns to be subdeacons within the church.

Anointing with oil, often called "unction", is one of the mysteries administered by the Orthodox Church and it is not reserved only for the dying or terminally ill, but for all in need of spiritual or bodily healing. In Greece, during the Ottoman occupation, it became the custom to administer this Mystery annually on Great Wednesday to all believers; in recent decades, this custom has spread to many other locations. It is often distributed on major feast days, or any time the clergy feel it necessary for the spiritual welfare of its congregation.

According to Orthodox teaching unction is based on the Epistle of James:

Following Jesus Christ's Great Commission to the apostles, Christianity spread rapidly throughout the Roman Empire. Paul and the Apostles traveled extensively throughout the Empire, including Asia Minor, establishing Churches in major communities, with the first churches appearing in Jerusalem and the Holy Land, then in Antioch, Ethiopia, Egypt, Rome, Alexandria, Athens, Thessalonica, Illyricum, and Byzantium, which centuries later would become prominent as the New Rome.^[164] Christianity in the Roman Empire met with considerable resistance, as its adherents would refuse to comply with the Roman state (even at the threat of death) in offering sacrifice to the pagan gods. Despite persecutions, the Christian Church spread. The persecution dissipated upon the conversion of Emperor Constantine I in 312 AD.^[164]

By the 4th century Christianity had spread to numerous regions. A number of influential schools of thought had arisen, particularly the Alexandrian and Antiochian philosophical approaches. Other groups, such as the Arians, had also managed to gain influence. However, their positions caused theological conflicts within the Church, thus prompting the Emperor Constantine to call for a great ecumenical synod in order to define the Church's position against the growing, often widely diverging, philosophical and theological interpretations of Christianity. He made it possible for this council to meet not only by providing a location, but by offering to pay for the transportation of all the existing bishops of the Church. Most modern Christian Churches regard this synod, commonly called the First Council of Nicaea or more generally the First Ecumenical Council,^[164][165] as of major importance.

Several doctrinal disputes from the 4th century onwards led to the calling of ecumenical councils. In the Orthodox Church, an ecumenical council is the supreme authority that can be invoked to resolve contested issues of the faith. As such, these councils have been held to resolve the most important theological matters that came to be disputed within the Christian Church. Many lesser disagreements were resolved through local councils in the areas where they arose, before they grew significant enough to require an ecumenical council.

There are seven councils authoritatively recognised as ecumenical:

There are also two other councils which are considered ecumenical by some Orthodox. All Orthodox agree that the decisions of these further councils are valid; the disagreement is only whether they carry sufficient importance to be considered truly ecumenical:

In addition to these councils there have been a number of other significant councils meant to further define the Orthodox position. They are the Synods of Constantinople, in 1484, 1583, 1755, 1819, and 1872, the Synod of Jassy (Iași) in 1642, and the Pan-Orthodox Synod of Jerusalem in 1672. Another council convened in June 2016 to discuss many modern phenomena including Modernism, other Christian confessions, Orthodoxy's relation with other religions and fasting disciplines.^[173]

Eastern Christian culture reached its golden age during the high point of the Byzantine Empire and continued to flourish in Ukraine and Russia, after the fall of Constantinople. Numerous autocephalous churches were established in Europe: Russia, Greece, Georgia and Ukraine, as well as Asia.

In the 530s the Church of the Holy Wisdom (Hagia Sophia) was built in Constantinople under Emperor Justinian I.^[174]

There are the "Nestorian" churches resulted from the reaction of the Council of Ephesus (431), which are the earliest surviving Eastern Christian churches that keep the faith of only the first two ecumenical councils, i.e., the First Council of Nicaea (325) and the First Council of Constantinople (381) as legitimate. "Nestorian" is an outsider's term for a tradition that predated the influence of Nestorius, the origin of which might lay in certain sections of the School of Antioch or via Nestorius' teachers Theodore of Mopsuestia or Diodore of Tarsus. The modern incarnation of the "Nestorian Church" is commonly referred to as "the Assyrian Church" or fully as the Assyrian Church of the East.

The church in Egypt (Patriarchate of Alexandria) split into two groups following the Council of Chalcedon (451), over a dispute about the relation between the divine and human natures of Jesus. Eventually this led to each group anathematizing the other. Those that remained in communion with the other patriarchs (by accepting the Council of Chalcedon) are known today as the Greek Orthodox Church of Alexandria, where the adjective "Greek" refers to their ties to the Greek-speaking culture of the Byzantine Empire. However, those who disagreed with the findings of the Council of Chalcedon were the majority in Egypt, and today they are known as the Coptic Orthodox Church of Alexandria, having maintained a separate patriarchate. The Coptic Orthodox Church is currently the largest Christian church in Egypt and in the whole Middle East. There was also a similar, albeit smaller scale, split in Syria (Patriarchate of Antioch), which resulted in the separation of the Syriac Orthodox Church from the Byzantine Patriarchate of Antioch.

Those who disagreed with the Council of Chalcedon are sometimes called "Oriental Orthodox" to distinguish them from the "Eastern Orthodox", who accepted the Council of Chalcedon. Oriental Orthodox are also sometimes referred to as "non-Chalcedonians", or "anti-Chalcedonians". The Oriental Orthodox Church denies that it is monophysite and prefers the term "miaphysite", to denote the "united" nature of Jesus (two natures united into one) consistent with St. Cyril's theology: "The term union...signifies the concurrence in one reality of those things which are understood to be united" and "the Word who is ineffably united with it in a manner beyond all description" (St. Cyril of Alexandria, On the Unity of Christ). Both the Eastern Orthodox and Oriental Orthodox churches formally believe themselves to be the continuation of the true church, although over the last several decades there has been considerable reconciliation and the prospect of reunification has been discussed.

In the 9th and 10th centuries, Christianity made great inroads into pagan Europe, including Bulgaria (864) and later Kievan Rus' (988). This work was made possible by the work of the Byzantine-era saints Cyril and Methodius. When king Rastislav of Moravia asked Byzantium for teachers who could minister to the Moravians in their own language, Byzantine emperor Michael III chose these two brothers. Cyril and Methodius translated the Bible and many of the prayer books. With time, as the translations prepared by them were copied by speakers of other dialects, the hybrid literary language Church Slavonic was created. Originally sent to convert the Slavs of Great Moravia, Cyril and Methodius were forced to compete with Frankish missionaries from the Roman diocese. Their disciples were driven out of Great Moravia in AD 886 and emigrated to Bulgaria.^[175]

After the Christianization of Bulgaria in 864, the disciples of saints Cyril and Methodius in Bulgaria, the most important being Saint Clement of Ohrid and Saint Naum of Preslav, were of great importance to the Orthodox faith in the First Bulgarian Empire. In a short time they managed to prepare and instruct the future Bulgarian clergy into the biblical texts and in AD 870 the Fourth Council of Constantinople granted the Bulgarians the right to have the oldest organised autocephalous Slavic Orthodox Church that little later, from autonomous Bulgarian archbishopric, became Patriarchate. The success of the conversion of the Bulgarians facilitated the conversion of East Slavic peoples, most notably the Rus', predecessors of Belarusians, Russians, and Ukrainians.^[176] Major event is the development of the Cyrillic script in Bulgaria at the Preslav Literary School in the 9th century. The Cyrillic script and the liturgy in Old Church Slavonic, also called Old Bulgarian, were declared official in Bulgaria in 893.^{[177][178][179]}

The work of the Thessaloniki brothers Cyril and Methodius and their disciples had a major impact to Serbs as well.^{[180][181][182][183][184][185][186][187]} However, they accepted Christianity collectively by families and by tribes (in the process between the 7th and the 9th century). In commemoration of their baptisms, each Serbian family or tribe began to celebrate an exclusively Serbian custom called Slava (patron saint) in a special way to honor the Saint on whose day they received the sacrament of Holy Baptism. It is the most solemn day of the year for all Serbs of the Orthodox faith and has played a role of vital importance in the history of the Serbian people. Slava is actually the celebration of the spiritual birthday of the Serbian people which the Church blessed and proclaimed it a Church institution.^[188]

The missionaries to the East and South Slavs had great success in part because they used the people's native language rather than Greek, the predominant language of the Byzantine Empire or Latin as the Roman priests did.^[180] Today the Russian Orthodox Church is the largest of the Orthodox Churches followed by the Romanian Orthodox Church.^[189]

In the 11th century what was recognised as the Great Schism took place between Rome and Constantinople, which led to separation between the Church of the West, the Catholic Church, and the Eastern Byzantine Churches, now the Orthodox. There were doctrinal issues like the filioque clause and the authority of the Roman Pope involved in the split, but these were greatly exacerbated by political factors of both Church and state, and by cultural and linguistic differences between Latins and Greeks. Regarding papal supremacy, the Eastern half grew disillusioned with the Pope's centralization of power, as well as his blatant attempts of excluding the Eastern half in regard to papal approvals. It used to be that the emperor would at least have say when a new Pope would be elected, but towards the high Middle Ages, the Christians in Rome were slowly consolidating power and removing Byzantine influence. However, even before this exclusionary tendency from the West, well before 1054, the Eastern and Western halves of the Church were in perpetual conflict, particularly during the periods of Eastern iconoclasm and the Photian schism.^[190]

The final breach is often considered to have arisen after the capture and sacking of Constantinople by the Fourth Crusade in 1204; the final break with Rome occurred circa 1450. The sacking of Church of Holy Wisdom and establishment of the Latin Empire as a seeming attempt to supplant the Orthodox Byzantine Empire in 1204 is viewed with some rancour to the present day. In 2004, Pope John Paul II extended a formal apology for the sacking of Constantinople in 1204, which was importantly also strongly condemned by the Pope at the time (Innocent III, see reference at end of paragraph); the apology was formally accepted by Patriarch Bartholomew of Constantinople. Many things that were stolen during this time—holy relics, riches, and many other items—were not returned and are still held in various European cities, particularly Venice.^[191][192]

Reunion was attempted twice, at the 1274 Second Council of Lyon and the 1439 Council of Florence. The Council of Florence briefly reestablished communion between East and West, which lasted until after the fall of Constantinople in 1453. In each case, however, the councils were rejected by the Orthodox people as a whole, and the union of Florence also became very politically difficult after Constantinople came under Ottoman rule. Some local Eastern churches have, however, renewed union with Rome in time since (see Eastern Catholic Churches). Recent decades have seen a renewal of ecumenical spirit and dialogue between the Churches.^[193]

In 1453, the Byzantine Empire fell to the Ottoman Empire. By this time Egypt had been under Muslim control for some seven centuries, but Orthodoxy was very strong in Russia which had recently acquired an autocephalous status; and thus Moscow called itself the Third Rome, as the cultural heir of Constantinople.

Under Ottoman rule, the Greek Orthodox Church acquired substantial power as an autonomous millet. The ecumenical patriarch was the religious and administrative ruler of the Rûm (Ottoman administrative unit meaning "Roman"), which encompassed all the Orthodox subjects of the Empire.

Up until 1666, when Patriarch Nikon was deposed by the tsar, the Russian Orthodox Church had been independent of the State.^[194] In 1721 the first Russian Emperor, Peter I abolished completely the patriarchate and so the church effectively became a department of the government, ruled by a most holy synod composed of senior bishops and lay bureaucrats appointed by the Emperor himself. From 1721 until the Bolsheviks' October Revolution of 1917, the Russian Orthodox Church was essentially transformed into a governmental agency, a tool used to various degrees by the tsars in the imperial campaigns of Russification. The church was allowed by the State to levy taxes on the peasants. Therefore, the church, along with the imperial regime, to which it belonged, came to be presented as an enemy of the people by the Bolsheviks and the other Russian revolutionaries.^[195]

After the October revolution of 1917, part of the clergy of the Russian Church escaped the Bolshevik persecutions by fleeing abroad, where they founded an independent church in exile, reunified with the Russian one in 2007. The Orthodox Church clergy in Russia were seen as sympathetic with the cause of the White Army in the Civil War after the Revolution, and occasionally collaborated with it; Patriarch Tikhon's declared position was vehemently anti-Bolshevik in 1918. This may have further strengthened the Bolshevik animus against the church. The Soviet government confiscated church property, ridiculed religion, harassed believers, and propagated atheism in schools. Actions toward particular religions, however, were determined by state interests, and most organised religions were never outlawed. Some actions against Orthodox priests and believers along with execution included torture, being sent to prison camps, labour camps or mental hospitals.^[196][197] In the first five years after the Bolshevik revolution, 28 bishops and 1,200 priests were executed.^[198]

After Nazi Germany's attack on the Soviet Union in 1941, Joseph Stalin revived the Russian Orthodox Church to intensify patriotic support for the war effort. By 1957 about 22,000 Russian Orthodox churches had become active. However, in 1959, Nikita Khrushchev initiated his own campaign against the Russian Orthodox Church and forced the closure of about 12,000 churches. It is estimated that 50,000 clergy had been executed between the revolution and the end of the Khrushchev era. Members of the church hierarchy were jailed or forced out, their places taken by docile clergy, many of whom had ties with the KGB. By 1985 fewer than 7,000 churches remained active.^[198]

However, there is definitely marked return to Christian Orthodoxy in Russia. According to the Pew Research Religion & Public Life Project, between 1991 and 2008, the share of Russian adults identifying as Orthodox Christian rose from 31 percent to 72 percent, according to a new Pew Research Center analysis of three waves of data (1991, 1998 and 2008) from the International Social Survey Programme (ISSP) – a collaboration involving social scientists in about 50 countries.^[199]

Albania was the only state to have declared itself officially fully atheist.^[200] In some other Communist states such as Romania, the Romanian Orthodox Church as an organization enjoyed relative freedom and even prospered, albeit under strict secret police control. That, however, did not rule out demolishing churches and monasteries as part of broader systematization (urban planning), and state persecution of individual believers. As an example of the latter, Romania stands out as a country which ran a specialised institution where many Orthodox (along with people of other faiths) were subjected to psychological punishment or torture and mind control experimentation in order to force them give up their religious convictions. However, this was only supported by one faction within the regime, and lasted only three years. The Communist authorities closed down the prison in 1952, and punished many of those responsible for abuses (twenty of them were sentenced to death).^[201][202]

Eastern Orthodoxy represents the majority of Eastern Christianity. The Orthodox trace their bishops back to the apostles through apostolic succession, and continue the ancient Christian practices of veneration of saints, especially Mary as the Theotokos, prayers for the dead, and monasticism. Orthodoxy does not openly promote statuary, although it is not expressly condemned, instead limiting itself primarily to two-dimensional iconography. Western theological concepts of original sin, substitutionary atonement, predestination, purgatory and particular judgment are generally rejected by traditional Orthodox theologians.

The Orthodox believe themselves to be the One Holy Catholic and Apostolic Church, that is, the true Church established by Jesus Christ and placed into the care of the apostles. As almost all other Christian groups are in indirect schism with the Orthodox Church, mostly as a result of the Great Schism with the Catholic Church at the turn of the second Christian millennium (before the schisms of the Protestant Reformation), these other groups are viewed as being Christian, but who, to varying degrees, lack full theological orthodoxy and orthopraxy. As such, all groups outside of the Orthodox Church are not seen as being members of the church proper, but rather separated brethren who have failed to retain the fullness of the Christian faith and theology. These deviations from orthodoxy have traditionally been called heresy, but due to the term's perceived pejorative connotations, some prefer the more technical designation of the term heterodoxy.

In 1920, the Ecumenical Patriarchate of Constantinople, published an encyclical "addressed 'To all the Churches of Christ, wherever they may be', urging closer co-operation among separated Christians, and suggesting a 'League of Churches', parallel to the newly founded League of Nations".^[203] This gesture was instrumental in the foundation of the World Council of Churches (WCC);^[204] as such, almost all Eastern Orthodox churches are members of the WCC and "Orthodox ecclesiastics and theologians serve on its committees".^[205] Kallistos Ware, a British metropolitan bishop of the Orthodox Church, has stated that ecumenism "is important for Orthodoxy: it has helped to force the various Orthodox churches out of their comparative isolation, making them meet one another and enter into a living contact with non-Orthodox Christians."^[206]

Hilarion Alfeyev, Metropolitan of Volokolamsk and head of external relations for the Moscow Patriarchate of the Russian Orthodox Church, stated that Orthodox and Evangelical Protestant Christians share the same positions on "such issues as abortion, the family, and marriage" and desire "vigorous grassroots engagement" between the two Christian communions on such issues.^[207]

In that regard, the differences between the Catholic and Eastern Orthodox communions have not been improved in any relevant way. Dogmatic and liturgical polarities have been significant, even and especially in recent times. A pertinent point of contention between the monarchically papal, administratively centralised Catholic Church and the decentralised confederation of Orthodox churches is the theological significance of the Virgin Mary.^[208] Even during a visit by Pope Francis to Georgia in October 2016, the leader of the Catholics was snubbed by most Orthodox Christians when he was holding mass in front of the practically empty Mikheil Meskhi Stadium in Tbilisi.^[209]

The Oriental Orthodox churches are not in communion with the Eastern Orthodox Church, despite their similar names. Slow dialogue towards restoring communion between the two churches began in the mid-20th century,^[210] and, notably, in the 19th century, when the Greek Patriarch in Egypt had to absent himself from the country for a long period of time; he left his church under the guidance of the Coptic Pope Cyril IV of Alexandria.^[211]

Historically, the Orthodox Church and the non-Chalcedonians were among the first peoples to have contact with Islam, which conquered Roman/Byzantine Syria-Palestine and Egypt in the 7th century, and fought many battles against Islamic conquests. The Qur'an itself records its concurrent observations regarding the Roman world in Surah al-Rum. The main contact with Islam however, came after the conquest of the Seljuk Turks of Roman/Byzantine Anatolia in the 13th century.

Christians who were under Islamic rule were denied equality of rights and were forced to pay the Jizya poll tax.^[212]

In Russia, Metropolitan Alfeyev stated belief in the possibility of peaceful coexistence between Islam and Christianity as the two religions have never had religious wars in Russia.^[213]

The various autocephalous and autonomous synods of the Orthodox Church are distinct in terms of administration and local culture, but for the most part exist in full communion with one another. Presently, there are two communions that reject each other and, in addition, some schismatic churches not in any communion, with all three groups identifying as Eastern Orthodox.

The main traditional historical communion is divided into two groups—those who use the Revised Julian calendar for calculating fixed feasts and the Julian calendar for calculating movable feasts, and those who use the Julian calendar for all purposes. This second group may include congregations whose church allows them to choose, with the proviso that the choice remains in effect at least until the end of the church year. Also in communion are the Estonian and Finnish Orthodox churches who have a dispensation to use the Gregorian calendar for all purposes. Another group is referred to as True Orthodoxy (or Old Calendarists); they are those who, without authority from their parent churches, have continued to use the old Julian calendar, claiming that the calendar reform in the 1920s is in contravention of the ecumenical councils. Similarly, another group called the Old Believers, separated in 1666 from the official Russian Orthodox Church as a protest against church rite reforms introduced by Patriarch Nikon of Moscow. As Eastern Orthodox Christianity is both collegial and local in structure, there is no single organization called the "True Orthodox Church" nor is there official recognition among the "True Orthodox" as to who is properly included among them. While some unions have taken place even up to the present, the majority of True Orthodox are only secondarily concerned with reunion as opposed to preservation of Eastern Orthodox teaching.

The calendar question reflects the dispute between those who wish to use a calendar which is reformed yet not Gregorian (effectively gaining the perceived benefits of the Gregorian calendar without disregarding the three anathemas issued against it in the sixteenth century), something which opponents consider unnecessary and damaging to continuity, and those who wish to maintain the traditional ecclesiastical calendar (which happens to be based on the Julian calendar), arguing that such a modern change goes against 1900 years of church tradition and was in fact perpetrated without an ecumenical council, which would surely have rejected the idea.

The dispute has led to much acrimony, and sometimes even to violence. Following canonical precepts, some adherents of the old calendar have chosen to abstain from clerical inter-communion with those synods which have embraced the new calendar until the conflict is resolved. The monastic communities on Mount Athos have provided the strongest opposition to the new calendar, and to modernism in general, while still maintaining communion with their mother church.

The Russian Orthodox Church Outside Russia (ROCOR) has recently united with the Moscow Patriarchate; these two branches of the Russian Orthodox Church had separated from each other in the 1920s due to the subjection of the latter to the hostile Soviet regime (see Act of Canonical Communion).

The Orthodox Church is a communion of 14 autocephalous (that is, administratively completely independent) regional churches,^[214] plus the Orthodox Church in America and then-recently the Orthodox Church of Ukraine. The Orthodox Church in America is recognised as autocephalous only by the Russian, Bulgarian, Georgian, Polish and Czech-Slovak churches. In December 2018, representatives of two former non-canonical but then-recent mildly recognised Ukraine Orthodox churches, along with two metropolitans of the canonical, but not autocephalous Ukraine Orthodox Church of the Moscow Patriarchate, proclaimed the formation of the unified Orthodox Church of Ukraine. On 5 January 2019 it received the tomos of autocephaly (decree which defines the conditions of a church's independence) from the Ecumenical Patriarchate and thus received the place in the diptych.

Each church has defined geographical boundaries of its jurisdiction and is ruled by its council of bishops or synod presided by a senior bishop–its primate (or first hierarch). The primate may carry the honorary title of patriarch, metropolitan (in the Slavic tradition) or archbishop (in the Greek tradition).

Each regional church consists of constituent eparchies (or, dioceses) ruled by a bishop. Some churches have given an eparchy or group of eparchies varying degrees of autonomy (self-government). Such autonomous churches maintain varying levels of dependence on their mother church, usually defined in a tomos or other document of autonomy.

Below is a list of the 14 autocephalous Orthodox churches forming the main body of Orthodox Christianity, all of which are titled equal to each other, but the Ecumenical Patriarchate is titled the first among equals. Based on the definitions, the list is in the order of precedence and alphabetical order where necessary, with some of their constituent autonomous churches and exarchates listed as well. The liturgical title of the primate is in italics.

Within the main body of Eastern Orthodoxy there are unresolved internal issues as to the autonomous or autocephalous status and/or legitimacy of the following Orthodox churches, particularly between those stemming from the Russian Orthodox or Constantinopolitan churches:

True Orthodoxy separated from the mainstream communion over issues of ecumenism and calendar reform since the 1920s.^[216] The movement rejects the Ecumenical Patriarchate of Constantinople, the Moscow Patriarchate, and those churches in communion with them, accusing them of heresy and placing themselves under bishops who do the same. They adhere to the use of the old Julian calendar since antiquity, claiming that the calendar reform in the 1920s is in contravention of the ecumenical councils. True Orthodox writers have argued that in missionary areas such as the United States, Orthodox (SCOBA) membership numbers may be overstated, with the comparative number of True Orthodox as up to 15% of the Orthodox population, in Russia, it has been claimed by some clergy that up to a million Russians may be True Orthodox of different jurisdictions, though the total number is often cited at 1.7–2 million together.

There is no official communion of traditionalists. They often are local groups and are limited to a specific bishop or locality. The following is a list of the most prominent True Orthodox churches:

Old Believers are groups that do not accept liturgical reforms carried out in the Russian Orthodox Church by Patriarch Nikon in the 17th century. Although all Old Believers groups emerged as a result of opposition to the Nikonian reform, they do not constitute a single monolithic body. Despite the emphasis on invariable adherence to the pre-Nikonian traditions, the Old Believers feature a great diversity of groups that profess different interpretations of the church tradition and often are not in communion with each other (some groups even practise re-baptism before admitting a member of another group into their midst).

Churches with irregular or unresolved canonical status are entities that have carried out episcopal consecrations outside of the norms of canon law or whose bishops have been excommunicated by one of the 14 autocephalous churches. These include nationalist and other schismatic bodies such as the Abkhazian Orthodox Church, Evangelical Orthodox Church, and Russian True Orthodox Church.