The interval set of symbols is a symbol used to represent intervals in mathematics, which is usually used to describe the characteristics of a group of real numbers. According to different characteristics and uses, the symbols of interval sets can be divided into the following types:

1. Open interval symbol ((a, b)): indicates a set of real numbers excluding endpoints A and B, that is, (a, b) = {x | a.

2. Closed interval symbol ([a, b]): indicates the set of real numbers including endpoints A and B, that is, [a, b]={x|a≤x≤b}.

3. Semi-open and semi-closed interval symbol ([a, b]): It represents a set of real numbers including endpoint A but not endpoint B, that is, [a, b] = {x | a ≤ x.

4. Semi-closed and semi-open interval symbol ((a, b)): It represents a group of real numbers including endpoint b but not endpoint a, that is, (a, b) = {x | a.

5. Left-closed right-open interval symbol ([a, b] or (a, b)): indicates a group of real numbers including the endpoint A but not the endpoint B, that is, [a, b] = {x | a ≤ x.

6. Left-open and right-closed interval symbol ((a, b) or [a, b]): indicates a group of real numbers including endpoint b but not endpoint a, that is, (a, b) = {x | a.

7. Single-dot interval symbol ((a) or [a]): It means a set of real numbers with only one endpoint A, that is, (a)={x|x=a} or [a]={x|x=a}.

8. Empty set symbol (_): indicates a group of real numbers without any elements, that is, _ = {}.

Interval sets of these symbols are often used in mathematics, which can help us describe and express the characteristics and relationships of real number sets more clearly. Reasonable use of these symbols can make mathematical reasoning and calculation more convenient.