tauon/ˈtaʊɑn/EtymologyFrom tau + -on, named after the Greek letter ταῦ (taû), the initial letter of Ancient Greek τρίτος (trítos, “third”), being the third lepton discovered.nounAn unstable elementary particle which is a type of lepton, having a mass almost twice that of a proton, a negative charge, and a spin of ½; it decays into hadrons (usually pions) or other leptons, and neutrinos.