By the end of Archaic Greece and early Classical Greece in the 5th century BC, the central west coast of Asia Minor, along with the islands of Chios and Samos, formed the heartland of Ionia proper. The Ionic dialect was also spoken on islands across the central Aegean and on the large island of Euboea north of Athens. The dialect was soon spread by Ionian colonization to areas in the northern Aegean, the Black Sea, and the western Mediterranean, including Magna Graecia in Sicily and Italy.
The Ionic dialect is generally divided into two major time periods, Old Ionic (or Old Ionian) and New Ionic (or New Ionian). The transition between the two is not clearly defined, but 600 BC is a good approximation.
The works of Homer (The Iliad, The Odyssey, and the Homeric Hymns) and of Hesiod were written in a literary dialect called Homeric Greek or Epic Greek, which largely comprises Old Ionic, with some borrowings from the neighboring Aeolic dialect to the north. The poet Archilochus wrote in late Old Ionic.
Ionic acquired prestige among Greek speakers because of its association with the language used by both Homer and Herodotus and the close linguistic relationship with the Attic dialect as spoken in Athens. This was further enhanced by the writing reform implemented in Athens in 403 BC, whereby the old Attic alphabet was replaced by the Ionic alphabet, as used by the city of Miletus. This alphabet eventually became the standard Greek alphabet, its use becoming uniform during the Koine era. It was also the alphabet used in the Christian Gospels and the book of Acts.
Proto-Greek e, o > East/Central Ionic ei, ou:[note 1] compensatory lengthening after loss of w in the sequences enw-, erw-, onw-, orw-. In Attic and West Ionic, e, o are not lengthened. (“East” refers to the Ionic of Anatolia, “Central” refers to the Ionic of the Cyclades, and “West” refers to the Ionic of Euboea.)
Proto-Greek *kʷ before o > Attic, West/Central Ionic p, some East Ionic k.
Proto-Greek *ťť > East/Central Ionic ss, West Ionic, Attic tt. This Ionic feature made it into Koine Greek.