The Greek alphabet

Earlier the Greeks took over all of the 22 letters of Phoenician.Five of them were reassigned to denote vowel sounds: the glide consonants j (yodh) and w (waw) were used for [i] (Ι, iota) and [u] (Υ, upsilon) respectively; the glottal stop consonant ʔ ('aleph) was used for [a] (Α, alpha); the pharyngeal ʕ (ʿayin) was turned into [o] (Ο, omicron); and the letter for h (he) was turned into [e] (Ε, epsilon).

Greek also introduced three new consonant letters for its aspirated plosive sounds and consonant clusters: Φ (phi) for /pʰ/, Χ (chi) for /kʰ/ and Ψ (psi) for /ps/. In western Greek variants, Χ was instead used for /ks/ and Ψ for /kʰ/ The origin of these letters is a matter of some debate.