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
Latin alphabet alphabets may discard letters, like the Rotokas alphabet, or add new letters, like the Danish and Norwegian alphabets. Letter shapes have evolved over the centuries, including the development in Medieval Latin of lower-case, forms which did not exist in the Classical period alphabet. English is the only major modern European language requiring no diacritics for native words (although a diaeresis may be used in words such as "coöperation"). It is generally believed that the Romans adopted the Cumae alphabet, a variant of the Greek alphabet, in the 7th century BC from Cumae, a Greek colony in Southern Italy. (Gaius Julius