A number is an abstract concept used for counting, marking or measuring.

Numbers are written symbols. Different counting systems can use the same number.

2, the classification is different

Numbers are divided into real numbers and imaginary numbers, which are expressed as I 2 =- 1. Real numbers are divided into rational numbers and irrational numbers, and irrational numbers are infinitely circulating decimals, such as √2, π. There is another kind of irrational number called transcendental number. Transcendental numbers are numbers that cannot be expressed by root signs, such as the famous constants π and E, and rational numbers are numbers that can be expressed by fractions. And rational numbers also have positive and negative points.

We call all nonnegative integers such as 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, … natural numbers. Forward extension of 1, 2, 3, …, 9, 10 gives a positive integer 1, 2, 3, …, 9, 10, … backward extension gives a negative integer …

The "0" between positive and negative integers is a neutral number.

Put them together to get …,-1 1,-10, -9, …, -3, -2,-1, 0, 1, 2, 3, …, 9,655.

Being called an integer can perform four operations on an integer: addition, subtraction, multiplication and division, which are called four operations. Integer, addition, subtraction, multiplication and division operations form a closed set of numbers, which is the research object of the ancient branch of mathematics "number theory"

3. Different types

Numbers: Arabic numerals, Roman numerals, etc.

Numbers: integers, fractions, negative numbers, irrational numbers, etc.

4. Different functions

Numbers are written symbols used to represent numbers.

"Number" is a concept to measure things. It is a conscious expression of objective quantity. "Number" originated from the symbols used by primitive humans to count and formed the symbols of natural numbers. It is one of the greatest inventions of human beings, and it is the basis for human beings to describe things accurately.