Definition:Square/Function/Definition 1

Definition
Let $\F$ denote one of the standard classes of numbers: $\N$, $\Z$, $\Q$, $\R$, $\C$.

The square (function) on $\F$ is the mapping $f: \F \to \F$ defined as:
 * $\forall x \in \F: \map f x = x \times x$

where $\times$ denotes multiplication.

Also see

 * Equivalence of Definitions of Square Function