Particles

Composition

Particles may be elementary or composite. Composite particles are composed of other particles. For example, protons are composed of quarks. By contrast, elementary particles (also called fundamental particles) are not made of other particles. According to our current knowledge, only a very small number of these exist, such as leptons, quarks, and gluons, although it is possible that some are composite in currently unknown ways. While composite particles can very often be considered point-like, although having internal structure, elementary particles have so far been found to have no structure.