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
Greek alphabet of these letters is a matter of some debate. Three of the original Phoenician letters dropped out of use before the alphabet took its classical shape: the letter Ϻ ("san"), which had been in competition with Σ ("sigma") denoting the same phoneme /s/; the letter Ϙ ("qoppa"), which was redundant with Κ ("kappa") for /k/, and Ϝ ("digamma"), whose sound value /w/ dropped out of the spoken language before or during the classical period. Greek was originally written predominantly from right to left, just like Phoenician, but scribes could freely alternate between directions. For a time, a writing style with