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
Archaic Greek alphabets Archaic Greek alphabets Many local variants of the Greek alphabet were employed in ancient Greece during the archaic and early classical periods, until they were replaced by the classical 24-letter alphabet that is the standard today, around 400 BC. All forms of the Greek alphabet were originally based on the shared inventory of the 22 symbols of the Phoenician alphabet, with the exception of the letter Samekh, whose Greek counterpart Xi () was used only in a sub-group of Greek alphabets, and with the common addition of Upsilon () for the vowel . The local, so-called "epichoric", alphabets differed in