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).

8.R+: positive real number set.

9.R-: negative real number set.

10, c: complex set.

1 1、? An empty set (a collection without any elements).

Extended data:

Properties of sets

1. Certainty: Every object can determine whether it is an element of a set. Without certainty, it cannot be a set. For example, "tall classmates" and "small numbers" cannot form a set. This property is mainly used to judge whether a set can constitute a set.

2. Relevance: Any two elements in the set are different objects. If it is written as {3,2,2}, it is equivalent to {2,3}. Being different from each other makes the elements in the collection not repeat. When two identical objects are in the same set, they can only be counted as an element of this set.

3. Disorder: {a, b, c}{c, b, a} are the same set.

4. Purity: the purity of the so-called set, such as set A = {x | x

5, integrity: still use the above example, all in line with X.

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