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 foreshadowed the development of vowel letters with a limited use of "matres lectionis", that is, consonants that pulled double duty as vowels, which for historical reasons occurred mostly at the ends of words. For example, the two letters "wāw" and "yōdh" stood for both the approximant consonants and , and the long vowels and in Phoenician. By this point in time, Greek had lost its sound, so Phoenician "yōdh" was used only for its vocalic value, becoming the Greek vowel letter iota . However, several Greek dialects still had a sound, and here "wāw" was used for both of its