In the standard model of particle physics the tau particles (e.g., tau leptons and tau neutrinos) are among the fundamental building blocks of matter.

The standard model attempts a comprehensive synthesis of fundamental particles and forces. According to the standard model, fermions (quarks and leptons) comprise all matter. There are twelve particles and twelve antiparticles in this class. In addition to the six known types of quarks (i.e., up, down, charm, strange, top, and bottom quarks) there are three charged leptons (the electron, the muon, and the tau particle), each with a corresponding neutral particle termed a neutrino. All of these fundamental particles have corresponding antiparticles that have exactly the same mass but which carry an opposite charge (i.e., the antiparticle of the electron is the positron and the antiparticle of the tau neutrino is the tau anti-neutrino). Fermions exist in three generations...