---
title: interval
---

An [interval](https://en.wikipedia.org/wiki/Interval_(mathematics)) is a range of numbers between two endpoints: closed, open, or half-open.

- A _closed_ interval, denoted by brackets, includes its endpoints. For example, [0,&nbsp;1]&nbsp;is the interval where `0 <= x <= 1`.

- An _open_ interval, denoted by parentheses, excludes its endpoints. For example, (0,&nbsp;1)&nbsp;is the interval where `0 < x < 1`.

- A _half-open_ interval includes only one of its endpoints. For example, (0,&nbsp;1]&nbsp;is the _left-open_ interval where `0 < x <= 1`, while [0,&nbsp;1)&nbsp;is the _right-open_ interval where `0 <= x < 1`.