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?