1, n: non-negative integer set or natural number set {0, 1, 2,3, ...}.

2, N* or N+: positive integer set {1, 2, 3, …}.

3, z: integer set {…,-1, 0, 1, …}.

4. Q: Rational number set.

5.Q+: the set of positive rational numbers.

6.Q-: set of negative rational numbers.

7.r: set of real numbers (including rational numbers and irrational numbers).

integer

Integer is the general name of all numbers in the sequence ...,-3,-2,-1,0,1,2,3, ...}, including negative integer, zero (0) and positive integer.

Like natural numbers, integers are a countable infinite set. Mathematically, this set is usually expressed as a bold Z or, which comes from the first letter of the German word Zahlen (meaning "number").

In algebraic number theory, these general integers belonging to rational numbers will be called rational integers to distinguish them from concepts such as Gaussian integers.