History of the Greek alphabet consonant letter, rather than seemingly have two exceptions in spelling. Greek, like Phoenician, made a distinction for vowel length; indeed, Greek had five short vowels and seven long vowels, but only five vowel letters. As in Phoenician, the difference in length was not originally made in writing. However, by the 6th century BC the letter eta (not needed for a consonant in eastern dialects of Greek, which lacked ) came to stand for the long vowel , and a new letter, omega, was developed for long . The provenance of omega is not known, but it is generally assumed to
History of the Greek alphabet (letter). In the 8th to 6th centuries, local or "epichoric" variants of the alphabet developed. They are classified into three main groups, following Adolf Kirchhoff (1887): green (Cretan), red (Euboean or Western) and blue (Ionic, Attic and Corinthian). The main distinction is in the supplemental signs added to the Phoenician core inventory. With the exception of the early Fayum alphabet, which does not fit into the tripartite scheme, all abecedaries add Υ to the Phoenician inventory. The green alphabets have only this; the red add Φ for , Χ for , and Ψ for ; and the blue add Φ