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
Xi (letter) dialects of most of the Greek mainland and Euboea, the sound [ks] was represented by Χ (which in classical Greek is chi, used for ). Because this variant of the Greek alphabet was used in Italy, the Latin alphabet borrowed Χ rather than Ξ as the Latin letter X. While having no Latin derivative, the Xi was adopted into the early Cyrillic alphabet, as the letter ksi (Ѯ, ѯ). The uppercase letter Ξ is used as symbol for: The lowercase letter ξ is used as a symbol for: These characters are used only as mathematical symbols. Stylized Greek text should