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
Greek alphabet neighboring (but otherwise "red") alphabet of Euboia: a form of that resembled a Latin "L" () and a form of that resembled a Latin "S" (). <nowiki>*</nowiki>Upsilon is also derived from waw (). The classical twenty-four-letter alphabet that is now used to represent the Greek language was originally the local alphabet of Ionia. By the late fifth century BC, it was commonly used by many Athenians. In 403 BC, at the suggestion of the archon Eucleides, the Athenian Assembly formally abandoned the Old Attic alphabet and adopted the Ionian alphabet as part of the democratic reforms after the overthrow of