1, union set: The set whose elements belong to A or B is called the union (set) of A and B, marked as A∪B (or B∪A), and read as A and B (or B and A), that is, A ∪ B = {x | x.

2. Intersection: The set with elements belonging to A and B is called the intersection (set) of A and B, marked as A∩B (or B∩A), and read as "A ∩ B" (or B ∩ A), that is, A ∩ B = {x |.

For example, the complete works U = {1, 2,3,4,5} A = {1,3,5} B = {1,2,5}. Then because both A and B have 1, 5, A ∩ B = {1, 5}.

3. Complement set: The set consisting of elements belonging to the complete set U but not to the set A is called the complement set of the set A, and is denoted as CuA, that is, CuA={x|x∈U, and x does not belong to A}.

A subset is a set of elements containing itself, and proper subset is a set of elements other than itself.

Subset: the range of set A is greater than or equal to set B, and set B is a subset of a; Proper subset: The range of the set A is larger than that of B, and B is the proper subset of A..

Example:

For example.

If the set A={ 1, 2}, then the subset of A is: empty set, {1}, {2}, {1, 2}.

Proper subset of A includes: empty set, {1}, {2}