# Functions¶

## Bijective¶

A function that is both surjective and injective.

## Concave¶

A function is concave if:

Contrast with convex.

## Convex¶

A function is convex if:

is an example of a convex function.

Contrast with concave.

## Domain¶

The set of points the function is defined for.

## Injective¶

A function is injective if it never maps two different inputs to the same output.