Characteristic of Greek literature is the variety of literary languages. However, except in Attica, Lesbos and Syracuse and sporadically elsewhere – in Boeotic we have the fragments of Corinna – the literature did not make use of the local language. In general it can be said that for each literary genre a language of its own was formed, independent of the native dialect of the individual writers, and that its development was determined by particular conditions. The most ancient form of Greek language known to us, the one in which the Homeric poems reached us, is an artificial product in which elements belonging to strongly divergent dialects appear – such as the Ionic, which constitutes its background, and the Aeolian of which holds numerous vestiges – and from different times. The language of the epos provided the dress for all hexametric poetry, from Hesiod to later times, and exerted an influence on Greek poetry in general. Not even the lesbian lyric, which the comparison with the epigraphic documents allows us to consider as the most adherent, among the poetic forms, to the maternal idiom of its followers, is completely immune from infiltrations of the epic dialect. The dialectal mixture stands out above all in the choral lyric, whose language can be defined as a generic Doric with superimposition of epic and aeolian elements at the same time. Ionia, which preceded the other regions in the development of civilization, was also the first to give itself a literary language distinct from local speakers. In Ionia the Greek fictional and scientific prose was born; and for a long time even native writers from other regions made use of the Ionian language. Under the influence of this is the oldest form, which has come down to us, of the Attic literary language, the dialogue of tragedy. Only towards the end of the century. V the language of the Attic writers becomes more adherent to the local dialect and soon becomes the literary language of all Greece.
The fortune of the Attic dialect has been decided since Athens became the spiritual capital of the Greeks. However, political reasons also contributed to its creation. Already in the century. V the attic begins to spread outside the natural borders as a language of communications between Athens and the confederate cities; and from the first years of the century. IV onwards gradually established itself as an official language in all the Ionian cities of the Aegean, even in those that had not been part of the Athenian maritime league. As it spreads, however, the attic changes, since the ionic population that adopts it retains some grammatical peculiarities (especially phonetic, such as ss instead of tt, rs instead of rr) and lexicals of its own dialect, and thus modified it spreads to other Greek lands and following the victorious path of Alexander it becomes the international language of the classical East. The spread of this now common language (κοινὴ διάλεκτος) of Hellenism was partly hindered for a time (about 250-50 BC) by the so-called Acheo-Doric koin ḗ formed in western Greece and as a language of the Aetolian and of the Achaean league that has penetrated into other regions, for example. in Arcadia. Another koin ḗ, more properly Doric, remained in use until the imperial age in the Doric islands of the Aegean. But eventually the ancient dialects disappear. The precise history of their regression has not yet been written; but we can think that around 500 d. C. were almost all extinct. The Laconian dialect had to resist longer than others, judging by the fact that some of its peculiarities still survive in speaking of the Zaconi, who inhabit a mountainous stretch of the Peloponnese. That the unification of the language in the Hellenistic age was not a purely literary phenomenon results from the fact that today’s Greek dialects – with the exception just indicated – are not the continuation of the ancients, but suppose as a basis an approximately uniform language, a koiné spoken. We do not have true and proper documents for this. Its characteristics are largely revealed to us by familiar scriptures (letters, counts, etc.) preserved in numerous papyri, from private inscriptions, and in literature especially from biblical texts (Old Testament version called the Seventy and New Testament). The nature and essence of koiné has been discussed and discussed among scholars. As we have seen, literary koiné is essentially an Attic language with Ionic infiltrations; the contribution of the other dialects is negligible. What the koiné speech has received different coloring in the individual regions due to the influence of local dialects is obvious, but determining the degree and manner of this influence is not easy. The Thumb reduces the dialectal element to a minimum even in the spoken language, while Kretschmer considers it so remarkable that he does not hesitate to attribute to it the character of a mixed language.
In the last centuries a. C. and in the first d. C. the Greek makes a series of innovations that give it a very different aspect from the ancient. For example, accentuating a tendency that in some dialect (especially in Boeotic) had manifested itself very early, the diphthongs αι, ει (which in the Attic had passed to ē already in the 5th century, if not earlier), οι and the vowel ē (η, ῃ) reduce to e, i, ü, i respectively. The long diphthongs ā i, ō i they lose the second element. Spirant consonants develop, unknown to ancient Greek and frequent in modern. The accent, which was previously musical, becomes expiratoris (intensive) and at the same time the difference between short and long vowels disappears. The use of prepositions is extended, while that of the “cases” of the declension shrinks at the same time. As for the verb, it will be enough to remember the gradual elimination of the optative. These and other innovations take place at a different pace in the various Hellenistic regions. In general it can be said that in Egypt and Asia, that is, in countries where Greek was an imported language, the process was faster than in Greece. Thus, for example, while in the Egyptian papyri the exchange of αι with ε appears already around 150 BC. C., for the Attic the reduction of that diphthong is documented by the inscriptions only in the 10th century. II d. C.