In quantum mechanics, bosons (/ˈbsɒn/, /ˈbzɒn/) comprise one of two classes of particles, the other being fermions. The name boson was coined by Paul Dirac to commemorate the contribution of the Indian physicist Satyendra Nath Bose in developing, with Einstein, Bose–Einstein statistics—which theorizes the characteristics of elementary particles.Examples of bosons include fundamental particles (e.g., the Higgs boson, the four force-carrying gauge bosons of the Standard Model, and the still-theoretical graviton of quantum gravity); composite particles (e.g., mesons and stable nuclei of even mass number such as deuterium, helium-4, or lead-208); and some of quasiparticles (e.g. Cooper pairs, plasmons, and phonons).

An important characteristic of bosons is that their statistics does not restrict the number that can occupy the same quantum state. This property is exemplified in helium-4 when it is cooled to become a superfluid.In contrast, two fermions cannot occupy the same quantum space. Whereas the elementary particles that make up matter (i.e. leptons and quarks) are fermions, the elementary bosons are force carriers that function as the 'glue' holding matter together. This property holds for all particles with integer spin (s = 0, 1, 2 etc.) as an immediate consequence of the spin–statistics theorem.

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