Greek (Modern Greek: ελληνικά elliniká) is an Independent branch of the Indo-European family of languages, native to Greece, Cyprus and other parts of the Eastern Mediterranean and the Black Sea. It has the longest documented history of any living Indo-European Language, spanning more than 3000 years of written records.^[3] Its writing system has been the Greek alphabet for the major part of its history; other systems, such as Linear B and the Cypriot syllabary, were used previously.^[4] The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic, and many other writing systems.

The Greek language holds an important place in the history of the Western world and Christianity; the canon of ancient Greek literature includes works in the Western canon such as the epic poems Iliad and Odyssey. Greek is also the language in which many of the foundational texts in science, especially astronomy, mathematics and logic and Western philosophy, such as the Platonic dialogues and the works of Aristotle, are composed; the New Testament of the Christian Bible was written in Koiné Greek. Together with the Latin texts and traditions of the Roman world, the study of the Greek texts and society of antiquity constitutes the discipline of Classics.

During antiquity, Greek was a widely spoken lingua franca in the Mediterranean world, West Asia and many places beyond. It would eventually become the official parlance of the Byzantine Empire and develop into Medieval Greek.^[5] In its modern form, Greek is the official language in two countries, Greece and Cyprus, a recognised minority language in seven other countries, and is one of the 24 official languages of the European Union. The language is spoken by at least 13.2 million people today in Greece, Cyprus, Italy, Albania, and Turkey and by the Greek diaspora.

Greek roots are often used to coin new words for other languages; Greek and Latin are the predominant sources of international scientific vocabulary.

Greek has been spoken in the Balkan peninsula since around the 3rd millennium BC,^[6] or possibly earlier.^[7] The earliest written evidence is a Linear B clay tablet found in Messenia that dates to between 1450 and 1350 BC,^[8] making Greek the world's oldest recorded living language. Among the Indo-European languages, its date of earliest written attestation is matched only by the now-extinct Anatolian languages.

The Greek language is conventionally divided into the following periods:

In the modern era, the Greek language entered a state of diglossia: the coexistence of vernacular and archaizing written forms of the language. What came to be known as the Greek language question was a polarization between two competing varieties of Modern Greek: Dimotiki, the vernacular form of Modern Greek proper, and Katharevousa, meaning 'purified', a compromise between Dimotiki and Ancient Greek, which was developed in the early 19th century and was used for literary and official purposes in the newly formed Greek state. In 1976, Dimotiki was declared the official language of Greece, having incorporated features of Katharevousa and giving birth to Standard Modern Greek, which is used today for all official purposes and in education.^[12]

The historical unity and continuing identity between the various stages of the Greek language is often emphasised.

Although Greek has undergone morphological and phonological changes comparable to those seen in other languages, never since classical antiquity has its cultural, literary, and orthographic tradition been interrupted to the extent that one can speak of a new language emerging.

Greek speakers today still tend to regard literary works of ancient Greek as part of their own rather than a foreign language.^[13] It is also often stated that the historical changes have been relatively slight compared with some other languages.

According to one estimation, "Homeric Greek is probably closer to demotic than 12-century Middle English is to modern spoken English,"^[14] (Greek has seen fewer changes in 2700 years than English has in 900 years).

Greek is spoken by at least 13 million people, mainly in Greece, Albania and Cyprus, but also worldwide by the large Greek diaspora. Historically, there were traditional Greek-speaking settlements and regions in the neighbouring countries of Albania, Bulgaria, and Turkey, as well as in several countries in the Black Sea area, such as Ukraine, Russia, Romania, Georgia, Armenia, and Azerbaijan, and around the Mediterranean Sea, Southern Italy, Syria, Israel, Egypt, Lebanon, Libya and ancient coastal towns along the Levant. Particularly in Albania due to the immigration wave towards Greece today a significant percentage of the population can speak the Greek language, or at least has some basic knowledge of it. The language is also spoken by Greek emigrant communities in many countries in Western Europe, especially the United Kingdom and Germany, Canada, the United States, Australia, Argentina, Brazil, Chile, South Africa and others.

Greek is the official language of Greece, where it is spoken by almost the entire population.^[15] It is also the official language of Cyprus (nominally alongside Turkish).^[16] Because of the membership of Greece and Cyprus in the European Union, Greek is one of the organization's 24 official languages.^[17] Furthermore, Greek is officially recognised as a minority language in parts of Italy and official in Dropull and Himara (Albania) and as a minority language all over Albania,^[18] as well as in Armenia, Romania, and Ukraine as a regional or minority language in the framework of the European Charter for Regional or Minority Languages.^[19] Greeks are also a recognised ethnic minority in Hungary.

The phonology, morphology, syntax and vocabulary of the language show both conservative and innovative tendencies across the entire attestation of the language from the ancient to the modern period. The division into conventional periods is, as with all such periodisations, relatively arbitrary, especially because at all periods, Ancient Greek has enjoyed high prestige, and the literate borrowed heavily from it.

Across its history, the syllabic structure of Greek has varied little: Greek shows a mixed syllable structure, permitting complex syllabic onsets but very restricted codas.

It has only oral vowels and a fairly stable set of consonantal contrasts.

The main phonological changes occurred during the Hellenistic and Roman period (see Koine Greek phonology for details):

In all its stages, the morphology of Greek shows an extensive set of productive derivational affixes, a limited but productive system of compounding^[20] and a rich inflectional system. Although its morphological categories have been fairly stable over time, morphological changes are present throughout, particularly in the nominal and verbal systems. The major change in the nominal morphology since the classical stage was the disuse of the dative case (its functions being largely taken over by the genitive). The verbal system has lost the infinitive, the synthetically-formed future and perfect tenses and the optative mood. Many have been replaced by periphrastic (analytical) forms.

Pronouns show distinctions in person (1st, 2nd, and 3rd), number (singular, dual, and plural in the ancient language; singular and plural alone in later stages), and gender (masculine, feminine, and neuter) and decline for case (from six cases in the earliest forms attested to four in the modern language).^[21] Nouns, articles and adjectives show all the distinctions except for person. Both attributive and predicative adjectives agree with the noun.

The inflectional categories of the Greek verb have likewise remained largely the same over the course of the language's history but with significant changes in the number of distinctions within each category and their morphological expression.

Greek verbs have synthetic inflectional forms for:

Many aspects of the syntax of Greek have remained constant: verbs agree with their subject only, the use of the surviving cases is largely intact (nominative for subjects and predicates, accusative for objects of most verbs and many prepositions, genitive for possessors), articles precede nouns, adpositions are largely prepositional, relative clauses follow the noun they modify and relative pronouns are clause-initial. However, the morphological changes also have their counterparts in the syntax, and there are also significant differences between the syntax of the ancient and that of the modern form of the language. Ancient Greek made great use of participial constructions and of constructions involving the infinitive, and the modern variety lacks the infinitive entirely (instead having a raft of new periphrastic constructions) and uses participles more restrictively. The loss of the dative led to a rise of prepositional indirect objects (and the use of the genitive to directly mark these as well). Ancient Greek tended to be verb-final, but neutral word order in the modern language is VSO or SVO.

Modern Greek inherits most of its vocabulary from Ancient Greek, which in turn is an Indo-European language, but also includes a number of borrowings from the languages of the populations that inhabited Greece before the arrival of Proto-Greeks,^[23] some documented in Mycenaean texts; they include a large number of Greek toponyms. The form and meaning of many words have evolved. Loanwords (words of foreign origin) have entered the language, mainly from Latin, Venetian, and Turkish. During the older periods of Greek, loanwords into Greek acquired Greek inflections, thus leaving only a foreign root word. Modern borrowings (from the 20th century on), especially from French and English, are typically not inflected; other modern borrowings are derived from South Slavic (Macedonian/Bulgarian) and Eastern Romance languages (Aromanian and Megleno-Romanian).

Greek words have been widely borrowed into other languages, including English: mathematics, physics, astronomy, democracy, philosophy,, baptism, evangelist, etc. Moreover, Greek words and word elements continue to be productive as a basis for coinages: anthropology, photography, telephony, isomer, biomechanics, cinematography, etc. and form, with Latin words, the foundation of international scientific and technical vocabulary like all words ending with –logy ("discourse"). There are many English words of Greek origin.^[24]

Greek is an independent branch of the Indo-European language family. The ancient language most closely related to it may be ancient Macedonian,^[25] which many scholars suggest may have been a dialect of Greek itself, but it is so poorly attested that it is difficult to conclude anything about it.^[26] Independently of the Macedonian question, some scholars have grouped Greek into Graeco-Phrygian, as Greek and the extinct Phrygian share features that are not found in other Indo-European languages.^[27] Among living languages, some Indo-Europeanists suggest that Greek may be most closely related to Armenian (see Graeco-Armenian) or the Indo-Iranian languages (see Graeco-Aryan), but little definitive evidence has been found for grouping the living branches of the family.^[28] In addition, Albanian has also been considered somewhat related to Greek and Armenian by some linguists. If proven and recognised, the three languages would form a new Balkan sub-branch with other dead European languages.^[29]

Linear B, attested as early as the late 15th century BC, was the first script used to write Greek.^[30] It is basically a syllabary, which was finally deciphered by Michael Ventris and John Chadwick in the 1950s (its precursor, Linear A, has not been deciphered and most likely encodes a non-Greek language).^[30] The language of the Linear B texts, Mycenaean Greek, is the earliest known form of Greek.^[30]

Another similar system used to write the Greek language was the Cypriot syllabary (also a descendant of Linear A via the intermediate Cypro-Minoan syllabary), which is closely related to Linear B but uses somewhat different syllabic conventions to represent phoneme sequences. The Cypriot syllabary is attested in Cyprus from the 11th century BC until its gradual abandonment in the late Classical period, in favor of the standard Greek alphabet.^[31]

Greek has been written in the Greek alphabet since approximately the 9th century BC.

It was created by modifying the Phoenician alphabet, with the innovation of adopting certain letters to represent the vowels. The variant of the alphabet in use today is essentially the late Ionic variant, introduced for writing classical Attic in 403 BC. In classical Greek, as in classical Latin, only upper-case letters existed. The lower-case Greek letters were developed much later by medieval scribes to permit a faster, more convenient cursive writing style with the use of ink and quill.

The Greek alphabet consists of 24 letters, each with an uppercase (majuscule) and lowercase (minuscule) form. The letter sigma has an additional lowercase form (ς) used in the final position:

In addition to the letters, the Greek alphabet features a number of diacritical signs: three different accent marks (acute, grave, and circumflex), originally denoting different shapes of pitch accent on the stressed vowel; the so-called breathing marks (rough and smooth breathing), originally used to signal presence or absence of word-initial /h/; and the diaeresis, used to mark full syllabic value of a vowel that would otherwise be read as part of a diphthong. These marks were introduced during the course of the Hellenistic period. Actual usage of the grave in handwriting saw a rapid decline in favor of uniform usage of the acute during the late 20th century, and it has only been retained in typography.

After the writing reform of 1982, most diacritics are no longer used.

Since then, Greek has been written mostly in the simplified monotonic orthography (or monotonic system), which employs only the acute accent and the diaeresis. The traditional system, now called the polytonic orthography (or polytonic system), is still used internationally for the writing of Ancient Greek.

In Greek, the question mark is written as the English semicolon, while the functions of the colon and semicolon are performed by a raised point (•), known as the ano teleia (άνω τελεία). In Greek the comma also functions as a silent letter in a handful of Greek words, principally distinguishing ό,τι (ó,ti, "whatever") from ότι (óti, "that").^[32]

Ancient Greek texts often used scriptio continua ('continuous writing'), which means that ancient authors and scribes would write word after word with no spaces or punctuation between words to differentiate or mark boundaries.^[33] Boustrophedon, or bi-directional text, was also used in Ancient Greek.

Greek has occasionally been written in the Latin script, especially in areas under Venetian rule or by Greek Catholics. The term Frankolevantinika / Φραγκολεβαντίνικα applies when the Latin script is used to write Greek in the cultural ambit of Catholicism (because Frankos / Φράγκος is an older Greek term for West-European dating to when most of (Roman Catholic Christian) West Europe was under the control of the Frankish Empire). Frankochiotika / Φραγκοχιώτικα (meaning "Catholic Chiot") alludes to the significant presence of Catholic missionaries based on the island of Chios. Additionally the term Greeklish is often used when the Greek language is written in a Latin script in online communications.^[34]