(mathematics) A rectangle in the real plane which is an open set: i.e., which does not contain its edges. If the sides of the open rectangle are parallel to the plane's axes, then the open rectangle can be described as the Cartesian product of two open intervals.

(mathematics) an interval in the real number line which does not contain its supremum and infimum. If specified by a pair of real numbers, then it consists of all the points on the real line whose values lie strictly between those two real numbers.

plural of open set

(topology) A cover whose members are all open sets.

Disaster Management Open Platform for Emergency Networks. A system which provides interoperability interfaces for sharing of emergency-related information to vetted emergency management agencies.

plural of open relationship

A romantic and/or sexual relationship in which the people involved are permitted or tolerated to be available to have additional simultaneous romantic and/or sexual relationships.

A chess opening in which white begins by playing 1.c4, moving his queen bishop's pawn to the fourth rank.

A configuration of a mouth wherein the front top teeth are separated vertically from the front bottom teeth even while the back top teeth are resting directly upon the back bottom teeth.

plural of open bite