# Identity element

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neutral element, unit element, zero element

An element of an algebraic structure $S$, often denoted $1$, $I$ or $e$, with a specific property with respect to a binary operation $*$: $$\forall x \in S \ \ 1 * x = x * 1 = x\ .$$

Where the binary operation is written additively, the identity element may be denoted $0$ or $O$, and termed a zero element.

How to Cite This Entry:
Identity element. Encyclopedia of Mathematics. URL: http://www.encyclopediaofmath.org/index.php?title=Identity_element&oldid=35633