noun
identity function; identity operator
A mathematical function that returns its input unchanged. Used in algebra, set theory, and functional programming.
恒等関数 f(x) = x は、どんな入力もそのまま返す。
The identity function f(x) = x returns any input as is.
Compound of 恒等 (identity, equality) and 関数 (function). A modern mathematical term.