Refers to different things and feelings gathered or intertwined.

Liu Xiang's "Nine Sighs and Sorrow" said: "Tears streaming down your face, tears streaming down your face." There is a poem in Song Sushi's "With Hu Shenfu": "I am ashamed of what I have done so far." Ming Liuji's "Flower Heart" says: "hentai's sad clouds intersect, and Luo Jin's old scar is wet at night."

Math:

In fact, the intersection of two sets A and B is a set that contains all the elements belonging to A and B, but no other elements.

The intersection of a and b is written as "A ∩B" Formally, x belongs to A ∩B if and only if x belongs to a and x belongs to B.

For example, the intersection of sets {1, 2,3} and {2,3,4} is {2,3}. The number 9 does not belong to the prime set {2,3,5,7, 1 1} and the odd set {1, 3}.

If the intersection of two sets A and B is empty, that is, they have no common elements, then they do not intersect.

More generally, intersection operations can be performed on multiple collections at the same time. For example, the intersection of sets a, b, c and d is A ∩ B ∩ C ∩ D = A ∩ (B ∩ (C ∩ D)). Intersection operation satisfies the associative law, that is, A ∩ (.

The most abstract concept is the intersection of sets of arbitrary nonempty sets. If m is a non-empty set and its elements are also sets, then X belongs to the intersection of m if and only if it belongs to the element A of any m. 。

Total sum

In other branches of set theory and mathematics, the union of sets is a set composed of all the elements of these sets, but not other elements.

Basic definition

If A and B are sets, the union of A or B is a set that contains all elements of A and all elements of B and has no other elements. The union of a and b is usually written as "A ∪B".

Formally: X is an element of A ∪B if and only if X is an element of A or X is an element of B. 。