Psi (letter) Psi (letter) Psi (; uppercase ', lowercase '; "psi" ) is the 23rd letter of the Greek alphabet and has a numeric value of 700. In both Classical and Modern Greek, the letter indicates the combination /ps/ (as in English word "lapse"). For Greek loanwords in Latin and modern languages with Latin alphabets, psi is usually transliterated as "ps". The letter's origin is uncertain. It may or may not derive from the Phoenician alphabet. It appears in the 7th century BC, expressing /ps/ in the Eastern alphabets, but /kʰ/ in the Western alphabets (the sound expressed by Χ in the
History of the Greek alphabet History of the Greek alphabet The history of the Greek alphabet starts with the adoption of Phoenician letter forms and continues to the present day. The Greek alphabet postdates Linear B, the syllabic script that was used for writing Mycenaean Greek, by several centuries. This article concentrates on the early period, before the codification of the now-standard Greek alphabet. The Phoenician alphabet was strictly speaking one that was consistently explicit only about consonants, though even by the 9th century BC it had developed "matres lectionis" to indicate some, mostly final, vowels. This arrangement is much less suitable for Greek than