In mathematics, the arrow (which in LaTeX is called "\mapsto") is used to describe what a function does to an arbitrary input. It is commonly used in combination with colon-to notation, which describes what a function's domain and codomain are.

By itself, $\mapsto$ can be used to describe a function without naming it, and so is a way to describe anonymous functions in mathematics.

Examples

The function $f (x) = x^{2}$ from the real numbers to the real numbers can be described using a combination of colon-to notation and mapsto notation as

$f : R \to R$ $x \mapsto x^{2} .$

In one line, although this is less common,

$f : R ∋ x \mapsto x^{2} \in R .$

(see in notation).