A finite set, also known as a finite set, is a set composed of finite elements. The elements of a finite set can be numbered, that is, its elements can be numbered and written as: a 1, a2, a3 ..., an, all the elements have been counted, and the natural numbers from 1 to n have been used, and different elements have got different numbers.

Infinite set, also called infinite set, is neither empty nor equal to Mn = {1, 2, ..., n}, n ∈ n Infinite elements cannot be "numbered".

There are two ways to define a finite set.

One is a set of line segments equivalent to a natural number string, and an empty set is called a finite set; A set that is not a finite set is called an infinite set.

Another definition is non-empty sets and empty sets that are not equivalent to their own proper subset are called finite sets, and the set of non-finite sets is called infinite sets.