A lepton is one of two categories of fermion particles, which are those having spin 1⁄2 and a non-zero rest mass. The electron is the prototypical member of the lepton category, which also includes uncharged neutrinos, and 2 other generations of electrons (muon and tau). The electroweak framework provides the comprehensive model of the leptons in the Standard Model.
The charged leptons have an electrical charge of -1, and each have an antimatter particle with the opposite charge.
Table 1: charged leptons
| Name | Mass kg | Mass MeV/\(c^2\) | Mass ratio | Antiparticle | electron | \(9.1 \times 10^{-31}\) | 0.51 | 1 | positron | muon | \(1.88 \times 10^{-28}\) | 105.7 | 207 | antimuon | tau | \(3.17 \times 10^{-27}\) | 1,776 | 3,477 | antitau |
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The higher generations are unstable and rapidly decay back into an electron along with various neutrinos.
There are also 3 corresponding generations of neutrinos, which have much smaller mass differences. The antineutrinos differ only in their spin direction.