The other type of matter particles are the leptons.

There are six leptons, three of which have electrical charge and three of which do not. They appear to be point-like particles without internal structure. The best known lepton is the electron (e^-). The other two charged leptons are the muon() and the tau(), which are charged like electrons but have a lot more mass. The other leptons are the three types of neutrinos (). They have no electrical charge, very little mass, and they are very hard to find.

Quarks are sociable and only exist in composite particles with other quarks, whereas leptons are solitary particles. Think of the charged leptons as independent cats with associated neutrino fleas, which are very hard to see.

For each lepton there is a corresponding antimatter antilepton. Note that the anti-electron has a special name, the "positron."

Trivia: "Lepton" comes from the Greek for "small mass," but this is a misnomer. Why? [Answer]