在数学中，像是一个跟函数相关的用语。

令 是一由定义域 映射至到达域 的函数。

设 是定义域 的元素， 在 之下的像便是 。

设 是定义域 的子集， 在 之下的像便是

{ 对于有些 }

In mathematics, an image is the subset of a function's codomain which is the output of the function from a subset of its domain.

Evaluating a function at each element of a subset X of the domain, produces a set called the image of X under or through the function. The inverse image or preimage of a particular subset S of the codomain of a function is the set of all elements of the domain that map to the members of S.