A quark is an elementary particle sensitive to strong interaction. It forms the hadrons. There are six kinds of quark: the up quark (u), the down quark (d), the strange quark (s), the charm quark (c), the bottom quark (b) and the top quark top (t). The name quark was given to these particles by Murray Gell-Mann, and is from a poem in James Joyce's Finnegan's Wake. Quarks are fermions.