**^**"chi".*Oxford English Dictionary*(3rd ed.). Oxford University Press. September 2005. (Subscription or UK public library membership required.)**^**In statistics, the term chi-squared or has various uses, including the chi-squared distribution, the chi-squared test, and chi-squared target models.In algebraic topology, Chi is used to represent the Euler characteristic of a surface.

In neuroanatomy, crossings of peripheral nerves (such as the optic chiasm) are named for the letter Chi because of its Χ-shape.

^{[4]}In chemistry, the mole fraction

^{[5]}^{[6]}and electronegativity^{[7]}may be denoted by the lowercase .In physics, denotes electric or magnetic susceptibility.

In rhetoric, both chiastic structure (a literary device) and the figure of speech Chiasmus derive from their names from the shape of the letter Chi.

In mechanical engineering, chi is used as a symbol for the reduction factor of relevant buckling loads in the EN 1993, a European Standard for the design of steel structures.

In graph theory, a lowercase chi is used to represent a graph's chromatic number.