History of the Greek alphabet derive from omicron with a line drawn under it. Long and were written with the digraphs "ει" and "ου", respectively, whereas long and short , , were never distinguished in writing. In 403/2 BC, following the devastating defeat in the Peloponnesian War and the restoration of democracy, the Athenians voted to abandon the old Attic alphabet ("Pre-Euclidean alphabet") and to introduce a standardized variant of the eastern Ionic alphabet, after a proposal by archon Eucleides. This Euclidean alphabet included eta and omega, which concluded the process of adapting the Phoenician script so that all vowels could be written systematically, thus
History of the Greek alphabet becoming the first 'true' alphabet. Apparently, some thirty years later, the same alphabet was introduced to Boeotia, having been adopted perhaps a little earlier in Macedonia, and went on in the course of the 4th century to displace the local alphabets throughout the whole Greek-speaking world. The Ionic alphabet included a new letter, omega, at the end of the alphabet, and standardised the representation of various sounds that had varied from one dialect to another, as follows: The absence of a letter for was of no consequence for the Ionic dialects, but sometimes led to ambiguities in Attic, which had