The set of points contained in between two given constants and , i.e. satisfying the condition . An open interval does not contain the end points, and is denoted by , as distinct from the (closed) segment (a closed interval), which contains the end points, i.e. consists of the points , .
Many authors use the (increasingly popular) alternative to denote the open interval .
Interval, open. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Interval,_open&oldid=15890