Greek alphabet glottal ("heth") was borrowed in two different functions by different dialects of Greek: as a letter for /h/ (Η, heta) by those dialects that had such a sound, and as an additional vowel letter for the long (Η, eta) by those dialects that lacked the consonant. Eventually, a seventh vowel letter for the long (Ω, omega) was introduced. Greek also introduced three new consonant letters for its aspirated plosive sounds and consonant clusters: Φ ("phi") for , Χ ("chi") for and Ψ ("psi") for . In western Greek variants, Χ was instead used for and Ψ for . The origin
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