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 alphabet All of the names of the letters of the Phoenician alphabet started with consonants, and these consonants were what the letters represented, something called the acrophonic principle. However, several Phoenician consonants were absent in Greek, and thus several letter names came to be pronounced with initial vowels. Since the start of the name of a letter was expected to be the sound of the letter (the acrophonic principle), in Greek these letters came to be used for vowels. For example, the Greeks had no glottal stop or voiced pharyngeal sounds, so the Phoenician letters "’alep" and "`ayin" became Greek "alpha"