Extended data
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+: Positive Rational Number Set
6.Q-: set of negative rational numbers
7.r: set of real numbers (including rational numbers and irrational numbers)
8.R+: positive real number set
9.R-: negative real number set
10, c: complex set
1 1、? : empty set (a set without any elements)
Baidu Encyclopedia _ Complete Works (Mathematical Significance)