In particle physics, quarks are one of the two basic constituents of matter (the other Standard Model fermions are the leptons).

Antiparticles of quarks are called antiquarks. Quarks are the only fundamental particles that interact through all four of the fundamental forces. The word was borrowed by Murray Gell-Mann from the book Finnegans Wake by James Joyce, where seabirds give "three quarks", akin to three cheers (probably onomatopoetically imitating a seabird call, like "quack" for ducks).

The names of quark flavours (up, down, strange, charm, bottom, and top) were also chosen arbitrarily based on the need to name them something that could be easily remembered and used.

Image: The 6 quarks and their most likely decay modes. Mass decreases moving from right to left.