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What is the symbol of the set?
The set of symbols in mathematics: n, N+, z, q, r, c, etc.

1, n: non-negative integer set or natural number set {0, 1, 2,3, ...}

2, N* or N+: positive integer set {1, 2, 3, ...}

3, z: integer set {…,-1, 0, 1, …}

4. Q: Rational number set

5.Q+: Positive Rational Number Set

6.Q-: set of negative rational numbers

7.r: set of real numbers (including rational numbers and irrational numbers)

8.R+: positive real number set

9.R-: negative real number set

10, c: complex set

1 1、? : empty set (a set without any elements)

Set classification:

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 pronounced as A and B (or B and A), that is, A∪B={x|x∈A, or X.

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 crosses B" (or "B crosses A"), that is, A∩B={x|x∈A, X ∩.

Infinite set: Definition: A set containing infinite elements in a set is called an infinite set.

Finite set: let N+ be a positive integer, Nn={ 1, 2,3, ..., n}. If there is a positive integer n that makes the set A correspond to NN one by one, then A is called a finite set.

Difference: The set of elements belonging to A but not to B is called the difference between A and B (set).

Complement set: A 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}.