Bose-Einstein statistics, class of statistics that applies to elementary particles called bosons, which include the photon, pion, and the W and Z particles. Bosons have integral values of the quantum mechanical property called spin and are "gregarious" in the sense that an unlimited number of bosons can be placed in the same state. All of the particles that mediate the fundamental forces of nature are bosons. See elementary particles; Fermi-Dirac statistics; statistical mechanics.

Fermi-Dirac statistics, class of statistics that applies to particles called fermions. Fermions have half-integral values of the quantum mechanical property called spin and are "antisocial" in the sense that two fermions cannot exist in the same state. Protons, neutrons, electrons, and many other elementary particles are fermions. See Bose-Einstein statistics; elementary particles; statistical mechanics.