Function

Image of a function

In discussion of some function $f:A\to B$, the image of an object $x$ refers to the object $fx$.

The term "image" may also refer to the set of all images. I.e., the image or range of a function $f:A\to B$ can refer to the set $\{fx|x\in A\}$.

Preimage of a function

À propos some function $f:A\to B$, the preimage of some subset $B^{\prime }$ of $B$ is the subset $A^{\prime }$ of $A$ for which every $a\in A^{\prime }$ has an image in $B^{\prime }$