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 Two variants of the Phoenician alphabet had major impacts on the history of writing: the Aramaic alphabet and the Greek alphabet. The Phoenician and Aramaic alphabets, like their Egyptian prototype, represented only consonants, a system called an "abjad". The Aramaic alphabet, which evolved from the Phoenician in the 7th century BCE, to become the official script of the Persian Empire, appears to be the ancestor of nearly all the modern alphabets of Asia: By at least the 8th century BCE the Greeks borrowed the Phoenician alphabet and adapted it to their own language, creating in the process the first "true"