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The particle-physics term elementary particle refers to particles that have no well-accepted internal structure; basically what is well-accepted about them is the manner in which they interact with elementary particles, which is indicated by their quantum numbers. The standard model of particle physics lists and categorizes elementary particles, demonstrating their interrelationships. The types of particles considered elementary are subdivided into elementary fermions and elementary bosons, the former including quarks and leptons, and the latter, photons, weak bosons, gluons, and Higgs bosons. Leptons include electrons, muons, tau particles, and neutrinos.