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 these words. From the Eastern Greek alphabet, they borrowed Y and Z, which were added to the end of the alphabet because the only time they were used was to write Greek words. The Anglo-Saxons began using Roman letters to write Old English as they converted to Christianity, following Augustine of Canterbury's mission to Britain in the sixth century. Because the Runic "wen", which was first used to represent the sound 'w' and looked like a p that is narrow and triangular, was easy to confuse with an actual p, the 'w' sound began to be written using a double