The number of objects can't be negative, it can't be said to be -2 apples, and the number of objects is an integer, not half and a half. Therefore, the number used to represent the number of objects is a natural number.

The definition of natural number is: natural number is used to measure the quantity of things or express the order of things. That is, the numbers represented by the numbers 0, 1, 2, 3, 4, ...

2, an object is not represented by 0.

For example, there are no students in the classroom after class.

3,0 is the smallest natural number.

Natural number is a number used to represent the number of things to be measured or the order of things, so its minimum value can only be 0.

Extended data:

1. The set n of natural numbers refers to a set that meets the following conditions:

① There is an element in n, which is recorded as 1.

② Every element in n can find an element in n as its successor.

③ 1 is the successor of 0. ④0 is not the successor of any element.

⑤ Different elements have different successors.

⑥ (inductive axiom) Any subset m of n, if 1∈M, and as long as X is in M, it can be deduced that the successor of X is also in M, then M = N. ..

Second, the nature of natural numbers

1. You can define addition and multiplication for natural numbers.

Where the addition operation "+"is defined as:

a+0 = a；

A+S(x) = S(a +x), where S(x) stands for the successor of x.

2. Orderly.

The orderliness of natural numbers means that natural numbers can be arranged into a series starting from 0 without repetition or omission: 0, 1, 2, 3, … This series is called natural number series.

If the elements of a set can establish a one-to-one correspondence with a natural sequence or a part of a natural sequence, we say that the set is countable, otherwise it is uncountable.

3. Infinite. Natural number set is an infinite set, and the sequence of natural numbers can be written endlessly.

4. transitivity: let n 1, n2 and n3 be natural numbers, if n1>; N2, n2 & gtN3, then n1>; n3 .

5.Trigement: For any two natural numbers n 1, n2, there exist and only exist the following three relationships: n1> N2, n 1=n2 or n 1

6. Least number principle: There must be a minimum number in any nonempty set of natural number set.

Baidu Encyclopedia-Natural Numbers