# Injective

A function $f$ from set $A$ to set $B$ is called an injection and $f$ is said to be injective if each element in $A$ maps to a different element in $B$.

In symbols, $f$ is injective if $f(a)=f(b)$ implies that $a=b$.

An injective function is also known as a one-to-one or one-one (both read as ‘one to one’) function.