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 alphabet alphabet, in which vowels were accorded equal status with consonants. According to Greek legends transmitted by Herodotus, the alphabet was brought from Phoenicia to Greece by Cadmos. The letters of the Greek alphabet are the same as those of the Phoenician alphabet, and both alphabets are arranged in the same order. However, whereas separate letters for vowels would have actually hindered the legibility of Egyptian, Phoenician, or Hebrew, their absence was problematic for Greek, where vowels played a much more important role. The Greeks used for vowels some of the Phoenician letters representing consonants which weren't used in Greek speech.