Physics, Chem. (used with a sing. v.)
the science that deals with average properties of the molecules, atoms, or elementary particles in random motion in a system of many such particles and relates these properties to the thermodynamic and other macroscopic properties of the system. Also called statis'tical phys'ics, statis'tical thermodynam'ics. Cf. Maxwell-Boltzmann statistics, quantum statistics.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.