History of the Greek alphabet only required one. The history here is complicated, but basically "sāmekh" dropped out in certain dialects, and was reused to represent in others, while usage for the sound varied between "ṣādē" and "šin". The letter now known as sigma took its name from "sāmekh" but its form from "šin", while the letter San, which occurred in a few dialects only, took its name from "šin" but its place in the alphabet from "ṣādē". A further Greek letter of uncertain origin, sampi, is found occasionally, and may represent an affricate, such as . For the special case of zeta, see Zeta
Chi (letter) for the design of steel structures. In graph theory, a lowercase chi is used to represent a graph's chromatic number. Chi (letter) Chi (uppercase Χ, lowercase χ; ) is the 22nd letter of the Greek alphabet, pronounced or in English. Its value in Ancient Greek was an aspirated velar stop (in the Western Greek alphabet: /ks/). In Koine Greek and later dialects it became a fricative (/) along with Θ and Φ. In Modern Greek, it has two distinct pronunciations: In front of high or front vowels ( or ) it is pronounced as a voiceless palatal fricative , as