The Byzantine Rite, also known as the Greek Rite or Constantinopolitan Rite, is the liturgical rite used by the Eastern Orthodox Church, the Greek/Byzantine Catholic churches, and in a modified form, Byzantine Rite Lutheranism.^[23][24] Its development began during the fourth century in Constantinople and it is now the second most-used ecclesiastical rite in Christendom after the Roman Rite.

The Byzantine Rite was originally developed and used in Greek language and later, with introduction of Eastern Orthodoxy to other ethnic groups it was translated into local languages and continued further development. Historically, most important non-Greek variants of Byzantine Rite are: Byzantine-Slavonic and Byzantine-Georgian. The rite consists of the divine liturgies, canonical hours, forms for the administration of sacred mysteries (sacraments) and the numerous prayers, blessings and exorcisms developed by the Church of Constantinople.

Also involved are the specifics of church architecture, icons, liturgical music, vestments and traditions which have evolved over the centuries in the Eastern Orthodox Church and which are associated with this rite. Traditionally, the congregation stands throughout the whole service, and an iconostasis separates the sanctuary from the nave of the church. The faithful are very active in their worship, making frequent bows and prostrations, and feeling free to move about the temple (church) during the services. Also, traditionally, the major clergy and monks neither shave nor cut their hair or beards.

Scripture plays a large role in Byzantine worship, with not only daily readings but also many quotes from the Bible throughout the services. The entire psalter is read each week, and twice weekly during Great Lent. Fasting is stricter than in the Roman Rite. On fast days, the faithful give up not only meat, but also dairy products, and on many fast days they also give up fish, wine and the use of oil in cooking. The rite observes four fasting seasons: Great Lent, Nativity Fast, Apostles' Fast and Dormition Fast. In addition, most Wednesdays and Fridays throughout the year are fast days and many monasteries also observe Monday as a fast day.

There are two ancient liturgical traditions from which all of the Eastern Rites (plus the Gallican Rite in the West) developed: the Alexandrian Rite in Egypt and the Antiochene Rite in Syria. These two Rites developed directly from practices of the Early Church. Of these two traditions, the Rite of Constantinople developed from the Antiochene Rite. Prior to the see of Constantinople's elevation to the dignity of patriarch by the Second Ecumenical Council in 381, the primary jurisdiction in Asia Minor was the Patriarchate of Antioch. With the council's elevation of Constantinople to primacy in the East, with the words "The Bishop of Constantinople ... shall have the prerogative of honour after the Bishop of Rome; because Constantinople is New Rome",^[25] the Constantinopolitan Rite gradually came to be the standard usage in every place under its jurisdiction.

Because the Rite of Constantinople evolved as a synthesis of two distinct rites — cathedral rite of Constantinople called the "asmatiki akolouthia" ("sung services") and the monastic typicon of the Holy Lavra of Saint Sabbas the Sanctified near Jerusalem — its offices are highly developed and quite complex.

Further developments continued to occur, centered mostly around Constantinople and Mount Athos. Monasticism played an important role in the development of the rituals. In Constantinople, the work of the monastery of the Studion greatly enriched the liturgical traditions, especially with regard to the Lenten observance. Iconography continued to develop and a canon of traditional patterns evolved which still influences Eastern religious art to this day.

Historical events have also influenced the development of the liturgy. The great Christological and Trinitarian controversies of Late Antiquity are reflected in the glorifications of the Trinity heard in the numerous ekphonies encountered during the services. In response to Nestorius' attack on giving the title of Theotokos to the Virgin Mary, the Byzantines increased the use of the term in the liturgy, and now almost every string of hymns ends with one in her honour, called a theotokion.

All liturgical rites change and develop over time. As new saints are canonized, new hymns are composed; as new needs arise, new prayers are written. The rite also profits from the fact that the Christian East is not so centralized in ecclesiastical polity as the West. This allows for greater diversity, and as members of one church visit another, a natural cross-pollination occurs with resultant enrichment on all sides. In spite of its great emphasis on tradition, the Byzantine Rite comprises a constantly growing and expanding ritual, with room for local practice.

The tradition of the Church of Constantinople ascribes the older of its two main Divine Liturgies to St. Basil the Great (d. 379), Metropolitan of Cæsarea in Cappadocia. This tradition is confirmed by the witness of several ancient authors, some of whom were contemporaries.^[26][27][28] It is certain that St. Basil made a reformation of the Liturgy of his Church, and that the Byzantine service called after him represents his reformed Liturgy in its chief parts, although it has undergone further modification since his time.^[29] St. Basil himself speaks on several occasions of the changes he made in the services of Cæsarea.^[30][31] and other contemporary witnesses attest his arrangement of the services. Basil had as his goal the streamlining of the services to make them more cohesive and attractive to the faithful. He also worked to reform the clergy and improve the moral life of Christians. He shortened the services and wrote a number of new prayers. The most important work attributed to him is the Divine Liturgy of St. Basil. He took as his basis the Liturgy of St. James as it was celebrated at his time in the region of Cappadocia, as well as some liturgical elements recorded in the Apostolic Constitutions.^[29]

Over time, the Liturgy of Saint Basil gained wide usage in Asia Minor and Syria. Peter the Deacon mentions that Basil's Liturgy was "used by nearly the whole East".^[29] However, the Alexandrian rite uses another Liturgy which is also attributed to Saint Basil,^[32] so Peter the Deacon's reference may not be to the Liturgy of St. Basil used in the Byzantine Rite.

Saint Basil's liturgical work was continued by John Chrysostom, Archbishop of Constantinople (died c. 407) who wrote new (and shorter) prayers for the Divine Liturgy, as well as other prayers. The Divine Liturgy of St. John Chrysostom is the most common form of the liturgy used in the rite today.

This tradition has several forms of the Divine Liturgy (celebration of the Eucharist), three of which are in use everywhere that the Byzantine Rite is used: the Liturgy of St. Basil the Great, the Liturgy of St. John Chrysostom, and the Liturgy of the Presanctified Gifts.

The divine liturgy is normally not celebrated daily except in cathedrals and larger monasteries. However, most parishes and smaller monasteries serve the Liturgy on Saturdays, Sundays, and major feast days throughout the year.

When a bishop officiates, the divine liturgy has an expanded form with particular solemnity; though other services are also affected by being officiated by a bishop, none is more so than the liturgy.

The daily cycle begins with vespers^[1] and proceeds throughout the night and day according to the following table:

The typica is used whenever the divine liturgy is not celebrated at its usual time, i.e., when there is a vesperal liturgy or no liturgy at all. On days when the liturgy may be celebrated at its usual hour, the typica follows the sixth hour (or matins, where the custom is to serve the Liturgy then) and the Epistle and Gospel readings for the day are read therein;^[4] otherwise, on aliturgical days or when the Liturgy is served at vespers, the Typica has a much shorter form and is served between the ninth hour and vespers.^[5]

Also, there are Inter-Hours for the First, Third, Sixth and Ninth Hours. These are services of a similar structure to, but briefer than, the hours. their usage varies with local custom, but generally they are used only during the Nativity Fast, Apostles Fast, and Dormition Fast on days when the lenten alleluia replaces "God is the Lord" at matins, which may be done at the discretion of the ecclesiarch when the Divine Liturgy is not celebrated.

In addition to these public prayers, there are also private prayers prescribed for both monastics and laypersons; in some monasteries, however, these are read in church. These include Morning and Evening Prayers and prayers (and, in Russia, canons) to be prayed in preparation for receiving the Eucharist.

The full cycle of services are usually served only in monasteries, cathedrals, and other Katholika (sobors). In monasteries and parishes of the Russian tradition, the Third and Sixth Hours are read during the Prothesis ( Liturgy of Preparation); otherwise, the Prothesis is served during matins, the final portion of which is omitted, the Liturgy of the Catechumens commencing straightway after the troparion following the Great Doxology.

The Midnight Office is seldom served in parishes churches except at the Paschal Vigil as the essential office wherein the burial shroud is removed from the tomb and carried to the altar.

The sundry Canonical Hours are, in practice, grouped together into aggregates^[6] so that there are three major times of prayer a day: Evening, Morning and Midday.^[7] The most common groupings are as follows:

On the eves before Great Feasts and, in some traditions, on all Sundays, this grouping is used. However, the All-night vigil is usually abridged so as to not last literally "all-night" and may be as short as two hours; on the other hand, on Athos and in the very traditional monastic institutions, that service followed by the hours and Liturgy may last as long as 18 hours.

When the feast is a weekday (or, in the Russian tradition, on any day for Christmas, Theophany), Vespers (with the Liturgy in most instances) is served earlier in the day and so Great Compline functions much as Great vespers does on the vigils of other feast days.

Baptism 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, once in the name of each of the persons of the Holy 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.^[33] Properly a new name is given, which becomes the person's name.

Children of Orthodox families are normally baptized shortly after birth. Converts to Orthodoxy are usually formally baptized 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 baptize.^[34] In such cases, should the person survive the emergency, it is likely that the person will be properly baptized 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 grants the gift of the Holy Spirit through anointing with Holy Chrism.^[35] It is normally given immediately after baptism as part of the same service, but is also used to receive again lapsed members of the Orthodox Church.^[36] 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.^[37]

A baptized and chrismated Orthodox Christian is a full member of the Church and may receive the Eucharist regardless of age.^[37]

The sanctification of chrism may, in theory, be performed by any bishop at any time, but in longstanding practice is performed no more than once a year; by hierarchs most autocephalous while certain others obtain their chrism from another church. Anointing with it substitutes for the laying-on of hands described in the New Testament, the apostles having made the initial chrism, according to the prayer of consecration of chrism, laying their hands on it, to substitute for laying on of hands for sundry practices where only the apostles could perform said laying on of hands.^[38]

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.

Communion is given only to baptized Orthodox Christians who have prepared by fasting, prayer and confession and is administered with a spoon directly into the recipient's mouth from the chalice.^[39] From baptism young infants and children are carried to the chalice to receive holy communion.^[37]

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 are encouraged to increase their prayer rule, adding the prescribed prayers in preparation for communing. Finally, they will fast completely from food, drink, and sexual activity from the evening, interpreted in sundry locations as from arising from sleep, or midnight, or from sunset the previous evening.

When one who has committed sins repents of them, wishing 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, 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 priest lays his hands on the penitent's head while reciting the prayer of absolution.

Sin is 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 the Roman Catholic Church, 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.^[40][41] 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.^[42][43]

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".^[41] Love between wife and husband, as an icon of relationship between Christ and Church, is eternal.^[41]

The Church does recognize 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.^[44] Ecclesiastically divorced Orthodox (not civilly divorced only).

Widowed people, as well as divorcées, may remarry, but a different, penitential service is used, and 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.

Deacons and priests, however, may not remarry or, if he does, he is liaised.

Should a married deacon or priest die, it is common for his wife to 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 a first Marriage in the Orthodox Church has two distinct parts: the Betrothal 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.

The service of a remarriage is penitential.

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.

Bishops are always monks. Although someone who is not a monk may be elected to be a bishop, which frequently happens with widowed priests, he must receive a monastic tonsure before consecration to the episcopate. Deacons and priests, however, are typically married, and it is customary that only monks or married men be ordained. 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 when there is of a shortage of married priests, a monk-priest may be assigned to a parish.

A deacon or priest would have to abandon his orders, i.e., be liaised, to marry after ordination; it is common for widowed clergy to enter a monastery. Also, widowed wives of clergy, who are discouraged from remarrying, often become nuns when their children are grown.

Only men can take holy orders, although deaconesses had both liturgical and pastoral functions within the church.^[45] This has fallen out of practice, the last deaconess having been ordained in the 19th century; however, 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. (Catherine Clark (2017). "National Catholic Reporter." March–April 6, 2017. p. 7 )

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, and with reception of this sacrament comes forgiveness of sins. In Greece, during the Ottoman occupation, when parish priests were not allowed to hear confessions, it became the custom to administer this mystery annually on Great Wednesday to all believers so that all could commune the following days through Pascha. In recent decades, this custom has spread to many other locations.

Two main strata exist in the rite, those places that have inherited the traditions of the Russian Church which had been given only the monastic Sabbaite typicon which she uses to this day^[13] in parishes and cathedrals as well as in monasteries, and everywhere else where some remnant of the cathedral rite remained in use; therefore, the rite as practiced in monasteries everywhere resembles the Russian recension, while non-Russian non-monastic customs differs significantly. For example, in the Russian tradition, the "all-night vigil" is served in every church on Saturday nights and the eves of feast days (although it may be abridged to be as short as two hours) while elsewhere, it is usual to have matins on the morning of the feast; however, in the latter instance, vespers and matins are rather less abridged but the Divine Liturgy commences at the end of matins and the hours are not read, as was the case in the extinct cathedral rite of Constantinople.

Also, as the rite evolved in sundry places, different customs arose; an essay on some of these has been written by Archbishop Basil Krivoshein and is posted on the web.^[46]

Horologion (Ὡρολόγιον; Church Slavonic: Chasoslov, Часocлoвъ), or Book of Hours, provides the fixed portions of the Daily Cycle of services (Greek: ἀκολουθίαι, translit. akolouthiai) as used by the Eastern Orthodox and Eastern Catholic churches.

Into this fixed framework, numerous moveable parts of the service are inserted. These are taken from a variety of liturgical books:

Also some books for special occasions, such as the book for the great week- He Megale Ebdomas, the Dekapentaugoustarion for the 15. August, or the Eklogadion including certain excerpts. The Apostolike Diakonia of the Church of Greece and some Greek-orthodox bishops have also published certain old liturgies. Such as the Liturgy of St. James and other.

The fixed portion of the liturgical year begins on September 1. There is also a moveable Paschal cycle which is fixed according to the date of Pascha (Easter), by far the most important day of the entire year. The interplay of these two cycles, plus other lesser cycles influences the manner in which the services are celebrated on a day to day level throughout the entire year.

Traditionally, the Julian Calendar has been used to calculate feast days. Beginning in 1924, several autocephalous churches adopted, for fixed dates, the Revised Julian Calendar which is aligned with the Gregorian calendar; the Paschal cycle, however, continued to be calculated according to the Julian Calendar. Today, some churches and portions of some other churches continue to follow the Julian Calendar while others follow the Revised Julian (Eastern Orthodox) or Gregorian (usually the more Latinized Byzantine Catholic) Calendar. Among Eastern Orthodox, only the Orthodox Church of Finland has adopted the Western calculation of the date of Pascha (see computus); all other Orthodox Churches, and a number of Eastern Catholic Churches, as well as the Ukrainian Lutheran Church, celebrate Pascha according to the ancient rules.^[48]

Various cycles of the liturgical year influence the manner in which the materials from the liturgical books (above) are inserted into the daily services:

Each day of the week has its own commemoration:

Most of the texts come from the Octoechos, which has a large collections of hymns for each weekday for each of the eight tones; during great lent and, to a lesser degree, the pre-lenten season, the Lenten Triodion supplements this with hymns for each day of the week for each week of that season, as does the Pentecostarion during the pascal season. Also, there are fixed texts for each day of the week are in the Horologion and Priest's Service Book (e.g., dismissals) and the Kathismata (selections from the Psalter) are governed by the weekly cycle in conjunction with the season.

Commemorations on the Fixed Cycle depend upon the day of the calendar year, and also, occasionally, specific days of the week that fall near specific calendar dates, e.g., the Sunday before the Exaltation of the Cross. The texts for this cycle are found in the Menaion.

The commemorations on the Paschal Cycle (Moveable Cycle) depend upon the date of Pascha (Easter). The texts for this cycle are found in the Lenten Triodion, the Pentecostarion, the Octoechos and also, because the daily Epistle and Gospel readings are determined by this cycle, the Gospel Book and Apostle Book. The cycle of the Octoechos continues through the following great lent, so the variable parts of the lenten services are determined by both the preceding year's and the current year's dates of Easter.

The cycle of the eight Tones is found in the Octoechos and is dependent on the date of Easter and commences with the Sunday after (eighth day of) Easter, that week using the first tone, the next week using the second tone, and so, repeating through the week preceding the subsequent Palm Sunday.^[22]

The portions of each of the Gospels from the narration of the Resurrection through the end are divided into eleven readings which are read on successive Sundays at matins; there are hymns sung at Matins that correspond with that day's Matins Gospel.

Note: Georgian Byzantine-Rite Catholics are not recognized as a particular Church (cf. canon 27 ^[62] of the Code of Canons of the Eastern Churches).

It has also been employed, although less frequently, in the Anglican Communion, e.g., its being utilized by the Society for Eastern Rite Anglicanism.^[52]