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 of an upright and less ornamented style of writing more like Latin print. In 1982, the monotonic orthography was officially adopted, abandoning the rough and smooth breathings (since the sound had long since disappeared) and reducing the three types of accent mark to one (since the tone accent had been replaced by a stress accent). Greek pronunciation has also changed considerably since ancient times, but these changes have not been apparent from the orthography, which has remained conservative — see Greek alphabet for a summary of the current situation. The names of some letters were changed in order to distinguish