In order to make it easier and clearer for everyone to understand the relevant knowledge of the set, we will sort out and share the knowledge points such as the collection of symbols and the classification of the set for reference.

The set of all positive integers of the common symbol set (1) in mathematics is called a positive integer set, which is denoted as N*, Z+ or n+;

(2) The set of all negative integers is called negative integer set, which is denoted as z-;

(3) The set composed of all nonnegative integers is called the nonnegative integer set (or natural number set), and is denoted as n;

(4) The set composed of all integers is called integer set, and is denoted as z;

(5) The set of all rational numbers is called the set of rational numbers, which is denoted as Q;

(6) The set of all real numbers is called the set of real numbers, which is denoted as r;

(7) The set of all imaginary numbers is called the imaginary number set, and it is denoted as I;

(8) The set of complex numbers consisting of all real numbers and imaginary numbers is called complex number set, and it is recorded as c.

Classification (1) empty set of a set

There is a special set, which contains no elements and is called an empty set.

(2) subset

Let s and t be two groups. If all elements of S belong to T, S is said to be a subset of T. ..

(3) Intersection

A set consisting of the same elements belonging to A and B, marked as A∩B (or B∩A), pronounced as "A through B" (or "B through A").

(4) Trade unions

A set consisting of all elements belonging to set A or set B is marked as A∪B (or B∪A) and pronounced as "A and B" (or "B and A").

(5) Generator set

There is a set A, and the set consisting of all subsets of the set A is called the power set of the set A. ..

(6) Supplement

Relative complement set: A set of elements belonging to A but not to B, which is called B's relative complement set about A. ..

Absolute complement set: A's relative complement set about the complete set U is called the absolute complement set of A. ..