A mapping diagram is a diagram that visualizes a relation. The inputs are listed in one column, and the outputs in another column. Arrows are used to indicate which inputs correspond to which outputs.

This mapping diagram shows the relation $\{(\text{-} 2, \text{-} 2),$ $(\text{-} 1, 0),$ $(0, 2),$ $(2, \text{-} 2)\}.$