In math an interval represents the valid values between an upper limit and a lower limit. The lower limit and the upper limit are either denoted as inclusive (including the end-point) or exclusive (excluding the end point). For example, the interval between 3 and 7 (inclusive) is denoted as
The same interval with exclusive end points is denoted as . The parenthesis indicates that the end point is exclusive and the square bracket denotes that the end point is inclusive.
Finally, a interval can mix inclusive and exclusive end points.