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
Greek alphabet alternating right-to-left and left-to-right lines (called "boustrophedon", literally "ox-turning", after the manner of an ox ploughing a field) was common, until in the classical period the left-to-right writing direction became the norm. Individual letter shapes were mirrored depending on the writing direction of the current line. There were initially numerous local (epichoric) variants of the Greek alphabet, which differed in the use and non-use of the additional vowel and consonant symbols and several other features. Epichoric alphabets are commonly divided into four major types according to their different treatments of additional consonant letters for the aspirated consonants (/pʰ, kʰ/) and