Each of these fermions also has an anti-particle associated with it, so there are a total of 24 different fundamental fermions. The anti-particle is similar to the original particle, but with opposite electrical charge. The "up", "charm", and "top" quarks have electrical charge of +2/3. Their anti-particles have charge -2/3 (anti-up, anti-charm, anti-top). The other three quarks (down, strange and bottom) have charge -1/3, and their anti-particles have charge +1/3. The electron, muon, and tau leptons all have charge of -1, and their anti-particles (anti-electron or "positron", anti-muon, anti-tau) have charge +1. All the neutrinos and anti-neutrinos have charge 0. The main difference between quarks or leptons with the same charge is their mass.