Vapor ( US English) or vapour ( British English) is the gaseous state of matter. Although vapor and gas are frequently used interchangeably, vapor often carries the connotation of gaseous matter in a state of equilibrium with identical matter in a liquid or solid state. See the entry on vapor pressure for more information on this topic.
The constituent atoms or molecules of a vapor possess vibrational, rotational, and translational motion. More information can be found under the entry of the Kinetic theory of gases.
See also: Evaporation, Temperature
