A non-negative integer set is a specific set, which refers to the set of all natural numbers, and is often represented by the symbol n. A non-negative integer includes positive integers and zeros, and is a countable set. The set of all nonnegative integers is usually called the set of nonnegative integers (or natural number set). Non-negative integer sets include natural numbers such as 0, 1, 2 and 3. Mathematically, the set of non-negative integers is represented by the bold capital letter n. Non-negative integers include positive integers and zeros. A set of nonnegative integers is a countable set.
Natural number 1 is usually called unit. In N and N+, take any number, add the unit 1 to it, and the number obtained is called the successor of the number, and add 1 one by one from the smallest element, so that all other elements in the number set can be obtained indefinitely, and the smallest element is not the successor of any element.
Non-negative integer:
Natural number, non-negative (0 is not listed as a natural number in the textbook)/positive integer (1, 2,3,4 ...). One reason why people think that natural numbers do not contain zero is that people start with "one, two, three ..." instead of "zero, one, two, three ..." because it is unnatural.
Natural numbers usually have two functions: they can be used for counting (such as "there are seven apples"), see radix; It can also be used for sorting (such as "This is the third largest city in China"). See ordinal number.
The set of natural numbers is a countable infinite set with no upper limit. Mathematicians generally use n to represent it. (N* represents a natural number other than 0) There are addition and multiplication operations on the set of natural numbers, and the result of addition or multiplication of two natural numbers is still a natural number. You can also do subtraction or division, but the result of subtraction and division is not necessarily a natural number, so subtraction and division operations may not be established in the set of natural numbers.