Omega

[2] In phonetic terms, the Ancient Greek Ω represented a long open-mid back rounded vowel IPA: [ɔː], comparable to the "aw" of the English word raw in dialects without the cot–caught merger, in contrast to omicron which represented the close-mid back rounded vowel IPA: [o] , and the digraph ου which represented the long close-mid back rounded vowel IPA: [oː].

As the final letter in the Greek alphabet, omega is often used to denote the last, the end, or the ultimate limit of a set, in contrast to alpha, the first letter of the Greek alphabet; see Alpha and Omega.

It was introduced in the late 7th century BC in the Ionian cities of Asia Minor to denote a long open-mid back rounded vowel [ɔː].

It is a variant of omicron (Ο), broken up at the side (), with the edges subsequently turned outward (, , , ).

[3] The Dorian city of Knidos as well as a few Aegean islands, namely Paros, Thasos and Melos, chose the exact opposite innovation, using a broken-up circle for the short and a closed circle for the long /o/.