1, the meaning of set: a set is the sum of some different things, and people can realize these things and judge whether a given thing belongs to the whole.

2. The general research objects are collectively referred to as elements, and the whole composed of some elements is called set.

3. Element determinism: once the set is determined, it is determined whether an element belongs to this set: Yes orNo. Example: the highest mountain in the world, the four beauties in ancient China, and all the people in the classroom.

4. Reciprocity of elements: the elements in a given set are unique and unrepeatable. For example, a group of happy letters {h, a, p, y}.

5. Disorder of elements: the position of elements in a set can be changed, and changing the position does not affect the set. For example, {a, b, c} and {a, c, b} represent the same set.

6. Finite set: a set containing a limited number of elements.

7. Infinite set: a set containing infinite elements.

8. Empty set: A set without any elements.

9. Relationship between elements and sets: If an element is in a set, it belongs to this set. If an element is not in the collection, it does not belong to the collection.

10, concept of function: let a and b be non-empty number sets. If any number X in set A has a certain number f(x) corresponding to it according to a certain correspondence F, then F: A-B is called a function from set A to set B Note: y=f(x