Definition: Are finite ordered list of elements
Definition: are (unordered) collections of objects called elements or members of the set
Set is unordered and no duplicate.
Set cardinality 基数
Definition: is the number of elements of a set S, denoted |S|
Relation between two set
A=B：A is equal to B if A and B have the same elements
A is disjoint from B if and only if there is no element that is in both A and B.
A⊆B: A is a subset of B if and only if every element in A is in B
A 是 B的子集，当且仅当A中所有的元素都在B中
A⊂B: A is a proper subset of B if and only if A is a subset of B but B is not a subset of A.
proper subset ：真子集
Unary Set Operations 一元集合操作
Definition: is the set of all subsets of A
Definition: is the difference between the universal set and A
Binary set operations 二元集合操作
Definition: include all elements in A or in B or in A and B
Definition: all elements that are in A and in B
Definition:all elements that are in A but not
Definition:AXB is the set whose members are all possible ordered pairs (a, b) where a is a member of A and b is a member of B