Interval

An interval is a connected segment of the real line. It is defined by taking two points, <math>a</math> and <math>b</math> with <math>a < b</math> that are the endpoints of the interval. Then the interval is the set of all points between the two endpoints, sometimes including the endpoints themselves. An open interval includes neither endpoint, a closed interval includes both endpoints, and when just one endpoint is included the interval is called half-open or half-closed.