Intersection: refers to the method. Union: indicates the method ∨.

Intersection is the common part of both. This symbol is like a bowl on the table, which buckles the common part of the intersection of two sets, and it is like a bowl of rice, in which rice and vegetables are put (set set).

Not all the bowls that merged upward were carried in, but the bowls that crossed downward were buckled in.

Properties of union set

The federation has the following properties:

1、A∪A=A，A∪=A，A∪B=B∪A .

2. if A∩B=A, then A∈B, and vice versa.

3. if A∪B=B, then A∈B, and vice versa.

4. If x∈(A∩B), then x∈A and X ∈ B.

5. if x∈(A∪B), then x∈A, or x ∈ b.