# Image

### From Online Dictionary of Crystallography

Image (*Fr*); Immagine (*It*); 像 (*Ja*); صورة (*Ar*).

Let *X* and *Y* be sets, *f* be the function *f* : *X* → *Y*, and *x* be some member of *X*. Then the **image** of *x* under *f*, denoted *f*(*x*), is the unique member *y* of *Y* that *f* associates with *x*.

The **image** of a subset *A* ⊆ *X* under *f* is the subset of *Y* defined by

*f*[*A*] = {*y* ∈ *Y* | *y* = *f*(*x*) for some *x* ∈ *A*}.