Neutrino, elementary particle with no electrical charge emitted during the decay of other particles. The existence of the neutrino was first postulated by Wolfgang Pauli in 1930 to account for the conservation of energy in the beta decay process, but the particle was not actually detected until 1956. There are distinct types of neutrinos associated with the electron and the muon. All 3 are part of the class of elementary particles known as leptons. Each type of neutrino has a corresponding particle, called an antineutrino, which differs from its neutrino only in a quality known as spin. Neutrinos are stable particles, being created or destroyed only in interactions involving the weak nuclear force, one of the 4 fundamental forces of nature. In 1998, Japanese and American researchers were able to demonstrate that neutrinos do have mass, a fact which had been unknown previously.
See also: Lepton.