elementary particle

In physics, a subatomic particle that is not known to be made up of smaller particles, and so can be considered one of the fundamental units of matter. There are three groups of elementary particles: quarks, leptons, and gauge bosons.

Quarks are of 12 types: up, down, charm, strange, top (or truth), and bottom (or beauty), plus the antiparticles of each. They combine in groups of three to produce heavy particles called baryons, and in groups of two to produce intermediate-mass particles called mesons. They and their composite particles are influenced by the strong nuclear force. Leptons are particles that do not interact via the strong nuclear force. Again, there are 12 types: the electron, muon, tau; their associated neutrinos, the electron neutrino, muon neutrino, and tau neutrino; and the antiparticles of each. These particles are influenced by the weak nuclear force, as well as by gravitation and electromagnetism. Gauge bosons carry forces between other particles. There are four types: gluon, photon, intermediate vector bosons (W⁺, W^-, and Z), and graviton. The gluon carries the strong nuclear force, the photon the electromagnetic force, W⁺, W^-, and Z the weak nuclear force, and the graviton, as yet unobserved, the force of gravity (see forces, fundamental).