ASCII Character ΞGreek capital letter Xi
Xi is the name of the 14th letter of the Greek alphabet (uppercase Ξ, lowercase ξ; Greek: ξι), representing the voiceless consonant cluster IPA: [ks]. It is pronounced [ksi] in Modern Greek, and generally /zaɪ/ or /ksaɪ/ in English. In the system of Greek numerals, it has a value of 60. Xi was derived from the Phoenician letter samekh 𐤎. Xi is distinct from the letter chi, which gave its form to the Latin letter X. The Xi was adopted into the early Cyrillic alphabet, as the letter ksi (Ѯ, ѯ).