This language belongs to the western branch of the Indo‐European language group, along with the Germanic, Italic, and Celtic families. It evolved into a relatively distinct and unified language ca. 2000 BCE, when Indo‐European speakers mixed with earlier inhabitants in the Aegean area, especially on the Greek mainland. Extensive contact with Minoan culture ca. 1650–1450 BCE led to the development of the Mycenaean dialect recorded in the prealphabetic Linear B syllabary. With the collapse of Mycenaean civilization ca. 1250–1200 BCE, the Mycenaean dialect was largely replaced by Doric dialects, except in the interior mountainous region of the Peloponnese and in Cyprus, to which it spread. From the Doric dialects gradually developed Northwest Greek, comprising the dialects of Phocian, Locrian, and Elean, and the West Greek dialects, or Doric proper, including Laconian, Heraclean, Argolic, Corinthian, Megarian, Rhodian, Coan, Theran, Cretan, and other lesser dialects of the west, such as Syracusan and Corcyran. In the east, a dialect akin to Mycenaean, which had already reflected innovations characteristic of the east Greek dialects of classical times, evolved in the Cycladic area into historical Ionic, from which Attic later developed; and in Thessaly another dialect, which was the origin of Aeolic, spread by migrations to Boeotia and Lesbos, where it underwent further modifications through convergence with Ionic.

Only a few dialects were used in literature, and then generally in a somewhat artificial form not corresponding exactly to the spoken language. Further, these literary dialects were associated with certain classes of literature and were so used, regardless of the author's native dialect.

First and foremost among these was the Homeric dialect (well developed before 700 BCE), an amalgam of Ionic and Aeolic, a development of centuries of epic and bardic tradition based on a substratum of Mycenaean. The language of Hesiod (seventh century BCE) is substantially that of Homeric epic but with some Aeolic forms and peculiarities found in Doric and Boeotian. The epic dialect is also used, with some modifications, by elegiac and iambic poets, and to some extent it influenced all of Greek poetry.

The melic poets Alcaeus and Sappho wrote in the Lesbian dialect, with some traces of epic forms. Their language too was imitated by later writers, including Theocritus.

The language of the choral lyric is an artificial composite of Doric characteristics with the elimination of local features and some admixture of Lesbian and epic forms. It was used by the Boeotian Pindar and the Ionians Simonides and Bacchylides as well. The first prose writers were the Ionic philosophers of the sixth century BCE, and in the fifth century the historian Herodotus and Hippocrates of Cos, a Dorian, wrote in Ionic. With the political hegemony and intellectual supremacy of Athens, the Attic dialect became the language of drama, and by the end of the fifth century it was also used in prose, but earlier prose writers such as the historian Thucydides, the tragedians Aeschylus, Sophocles, and Euripides, and the comedian Aristophanes avoided Attic peculiarities. Among the other great Attic prose writers were the orators Lysias, Isocrates, Aeschines, and Demosthenes, the philosopher Plato, and the historian Xenophon.

Some few other dialects were cultivated in local literature, but the majority of dialects are known only from inscriptions and play no role in literature.

From the welter of classical dialects emerged the Koine. Also called Hellenistic Greek, koinē, “the common (dialect),” designates the prevalent form of the Greek language from the time of Alexander the Great (late fourth century BCE) to the Byzantine period (sixth‐seventh century CE). The Koine emerged largely through a process of leveling and assimilation. Based primarily upon the Attic dialect, the Koine also incorporated elements from other dialects, including Ionic, Doric, and Boeotian. Features peculiar to a single dialect tended to be lost in the formation of a universal Greek vernacular, while those shared by several important dialects left their mark on it. It was spread by the Macedonian conquests over a vast area and became the vehicle of communication for diplomacy and commerce. With the adoption of Hellenic culture it became established in the leading centers of Greek civilization. Its widespread use, especially by nonnative Greek speakers, led to extensive modifications in the living language, which is best preserved in more than fifty thousand papyri, ostraca, and inscriptions from the fourth century BCE to the eighth century CE.

This largely homogenous dialect continued to develop as a living language, but a literary form of the Koine was created in imitation of classical Attic idiom. Among the leading Koine authors using this elevated language were the historians Polybius, Diodorus Siculus, Josephus, and Arrian, the biographer Plutarch, the rhetorician Dionysus of Halicarnassus, the geographer Strabo, the philosophers Philodemus, Philo, and Epictetus, and the Sophists Lucian, Philostratus, and Philostratus the Younger. The Atticistic movement, an artificial revival of the classical language, flourished especially in the second century CE as a reaction to the natural developments and innovations of the spoken language that impinged increasingly upon even the literary form of the Koine.

Much more akin to the living Koine is biblical Greek. Hardly a unity in itself, the language of the various Greek translations of the Hebrew scriptures (see Septuagint), the writings of the New Testament, and the Jewish and Christian apocrypha and pseudepigrapha does not constitute a special Jewish dialect of the Koine, much less a language outside the mainstream of the development of Greek. But like the papyri, ostraca, and inscriptions from Egypt subject to extensive bilingual interference from Egyptian (Coptic), biblical Greek in varying degrees preserves a Semitic tone and flavor, adopts Semitic modes of speech, and reflects Semitic interference in grammar. It diverges from the rest of the Koine most noticeably in vocabulary, as it coins new words to express specifically biblical concepts or uses older terms with new Jewish or Christian meanings.

The Koine is the direct ancestor of medieval and Modern Greek, except for the Tsaconian dialect descended from classical Laconian. Although the Modern Greek vernacular language (dimotiki) contains very many Latin and especially Turkish loanwords and is itself split into numerous dialects, it represents the latest phase in the development of the Greek language over an unbroken period of some four thousand years. Alongside the Modern Greek vernacular, there is an archaizing form of the language called the katharevousa, which long served as the standard learned and literary language but no longer enjoys its former official status.

Francis T. Gignac