- the kinetic theory a theory of gases postulating that they consist of particles of negligible size moving at random and undergoing elastic collisionsIn full: the kinetic theory of gases
- A fundamental theory of matter that explains physical properties in terms of the motion of atoms and molecules. In kinetic theory, properties such as pressure and temperature are viewed as statistical properties of the overall behavior of large numbers of particles. For example, the pressure exerted by a gas on an object is the net result of the numerous collisions of the gas molecules against the object. See also pressure statistical mechanics temperature thermodynamics.