fermionn.
/ˈfəːmɪɒn/, U.S. /ˈfɛrmiˌɑn/, /ˈfərmiˌɑn/ Particle Physics.
Any particle which has a spin equal to half a whole number and a wave function that is antisymmetric (so that the particle obeys Fermi-Dirac statistics and the Pauli exclusion principle). Cf. boson n.In nature fermions occur as particles of matter. Examples include quarks, leptons (such as the electron), baryons (such as the proton and the neutron), and entities containing an odd number of any of these particles, such as the nucleus of a helium-3 atom.
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the world > matter > physics > quantum theory > quantum mechanics > symmetry, conserved properly > [noun] > statistics of > particle obeying
fermion1947
1947 P. A. M. Dirac Princ. Quantum Mech. (ed. 3) ix. 210 It leads to a special statistics, which was first studied by Fermi, so we shall call particles for which only antisymmetrical states occur in nature fermions.
1963 New Scientist 1 Aug. 255/1 Only one fermion can exist in a particular state at any given time.
1968 M. S. Livingston Particle Physics iii. 59 It is found experimentally that electrons, protons, and neutrons are all fermions and that they have intrinsic spin s = ½ (h/2π).
1981 D. H. Perkins in J. H. Mulvey Nature of Matter iv. 79 Quarks and leptons are considered to be the fundamental fermions..in nature.
1989 R. Penrose Emperor's New Mind (1991) vi. 277 All electrons are identical with one another in a different way from the way in which all photons are identical! The difference lies in the fact that electrons are fermions whereas photons are bosons.
2012 Times Educ. Suppl. (Nexis) 28 Sept. 18 Our best evidence for the Higgs came through detecting two photons created from a virtual loop of fermions that came into existence because of Heisenberg's Uncertainty Principle.
This entry has been updated (OED Third Edition, December 2013; most recently modified version published online March 2022).
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