A set of values of a function corresponding to a particular subset of a domain.
像，像点函数中与某一集合中特定变量相对应的变量
A set that includes a given and similar set as a subset.
子集包含一个给定的或相似的子集的集合
For a universal set, the set of all elements in the set that are not in a specified subset.
补集对任意一个集合，这个集合的所有元素不共存在于它的任一子集合
