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 of these letters is a matter of some debate. Three of the original Phoenician letters dropped out of use before the alphabet took its classical shape: the letter Ϻ ("san"), which had been in competition with Σ ("sigma") denoting the same phoneme /s/; the letter Ϙ ("qoppa"), which was redundant with Κ ("kappa") for /k/, and Ϝ ("digamma"), whose sound value /w/ dropped out of the spoken language before or during the classical period. Greek was originally written predominantly from right to left, just like Phoenician, but scribes could freely alternate between directions. For a time, a writing style with