Chi (letter)

Chi (uppercase/lowercase Χ χ) is the 22nd letter of the Greek alphabet. It is used to represent the "ch" sound (as in Scottish "loch" or German "Bauch") in Ancient and Modern Greek. In the system of Greek numerals, it has a value of 600. Letters that came from it include the Roman X and Cyrillic Х.

Greek alphabet
Αα Alpha Νν Nu Ββ Beta Ξξ Xi Γγ Gamma Οο Omicron Δδ Delta Ππ Pi Εε Epsilon Ρρ Rho Ζζ Zeta Σσς Sigma Ηη Eta Ττ Tau Θθ Theta Υυ Upsilon Ιι Iota Φφ Phi Κκ Kappa Χχ Chi Λλ Lambda Ψψ Psi Μμ Mu Ωω Omega
History
Archaic local variants Diacritics Ligatures Numerals ϛ (6) ϟ (90) ϡ (900)
Use in other languages
Bactrian Coptic Albanian
Related topics
Use as scientific symbols
Book Category Commons

In mathematics, the lowercase ${\displaystyle \chi }$ is used to represent characteristic function, chi-square distribution in statistics and Euler characteristic in geometry.[1][2]