Xi (letter) Xi (letter) Xi (uppercase Ξ, lowercase ξ; ) is the 14th letter of the Greek alphabet. It is pronounced in Modern Greek, and generally or in English. In the system of Greek numerals, it has a value of 60. Xi was derived from the Phoenician letter samekh . Xi is not to be confused with the letter chi, which gave its form to the Latin letter X. Both in classical Ancient Greek and in Modern Greek, the letter Ξ represents the sound . In some archaic local variants of the Greek alphabet, this letter was missing. Instead, especially 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