Definition:Identity (Abstract Algebra)/Left Identity

Definition
Let $\struct {S, \circ}$ be an algebraic structure. An element $e_L \in S$ is called a left identity :
 * $\forall x \in S: e_L \circ x = x$

Also known as

 * Left neutral element
 * Left unit

Also see

 * Definition:Right Identity
 * Definition:Identity Element