Ionic (or Ionian) dialect appears to have spread originally from the Greek mainland across the Aegean at the time of the Dorian invasions, around the 11th Century B.C.
By the end of the Greek Dark Ages in the 8th Century B.C, 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.
Ionic dialect is generally divided into two major time periods, Old Ionic (or Old Ionian) and New Ionic (or New Ionian). The exact transition between the two is not clearly defined, but 600 B.C. is a good approximation.
The Homeric works (the Iliad, the Odyssey, and the Homeric Hymns), and the works of Hesiod, were written in a literary dialect called Homeric Greek or Epic Greek, which consists largely of Old Ionic, with some borrowings from the neighboring Aeolic dialect to the north. The poet Archilochus wrote in late Old Ionic.
The main differences between the Ionic dialect (Old and New) and Classical Attic were the following:
In Ionic, the shift from long alpha to eta occurs in almost all words, whereas in Attic it does not occur after eta, iota, or rho. Example: Attic ??????? (ne-a-ni-as) versus Ionic ??????? (ne-?-ni-?s), a "young person". Often the simple vowel ? or o of Attic dialect appears in Ionic as a diphthong (?????, kour?, "young lady, girl", for ????, kor?; ??????, peiras "end, border" for ?????, peras)
In many cases Ionic turned Proto-Greek labiovelar sound /kw/ into /k/ rather than /p/ before back vowels. Example: Attic ???? (hop?s) versus Ionic ???? (ok?s), "the same way (as)". It is worth mentioning that similar divergent outcomes for /kw/ occurred also in Celtic and Italic branches of the Indo-European language family, for example between Latin and Oscan, as well as between P-Celtic (Welsh) and Q-Celtic (Irish) ? e.g. Welshpump, Bretonpemp, Cornishpymp vs. Gaeliccóig or cùig, Irishcúig, Manxqueig (note the treatment of the same consonant in English with this word meaning "five ").
Ionic contracted adjoining vowels much less frequently than Attic. Example: Ionic ????? (gen-e-a) versus Attic ???? (gen-?), "family, stock".
Ionic "ss" appears as "tt" in later Classical Attic. Example: Ionic ???????? (tessares) versus Attic ???????? (tettares), "four".
Ionic had a very analytical word-order, perhaps the most analytical one within ancient Greek dialects. Moreover the Ionic morphology of noun and verb doesn't have dual-forms.
In some words, Attic initial aspiration was lacking in Old Ionic (the so called "psilosis"), and in New Ionic initial aspiration was probably lost entirely. Example: Attic ????? (hippos) versus Ionic ????? (ikkos), "horse".
p?los thick wine,lees (Attic ????? pelos mud,silt) (proverbial phrase mê dein ton OineaPêlea poiein , don't make wine into lees, Ath.9.383c, cf. Demetr.Eloc.171)
rhêchiê flood-tide , loanword to Attic as rhachia (Homeric,Koine,Modern Greek plêmmuris -ida)