Leptons are subatomic, elementary particles which are subject to the electromagnetic force, gravitational force, and weak interaction but do not take part in the strong interaction. They are spin-1/2 particles, i.e. fermions and therefore subject to the Pauli exclusion principle. Electrons are leptons, along with muons and tau leptons and their respective antiparticles. These all have an associated charge. There are also electrically-neutral leptons, the neutrinos, which are massless.