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Interval
An interval consists of all numbers that are between two endpoints.
Explanation
There are open and closed intervals.
Example 1
The argument of a complex number z in the open interval [0, 2π) is called the principle value. The interval (−π, π] can also be taken.
Example 2
The unit interval is the set of all real numbers greater than or equal to 0 and less than or equal to 1, and forms the closed interval [0,1].