Quarks

[kwawrk, kwahrk] /kwɔrk, kwɑrk/

noun
1.
Physics. any of the hypothetical particles with spin 1/2, baryon number 1/3, and electric charge 1/3 or −2/3 that, together with their antiparticles, are believed to constitute all the elementary particles classed as baryons and mesons; they are distinguished by their flavors, designated as up (u), down (d), strange (s), charm (c), bottom or beauty (b), and top or truth (t), and their colors, red, green, and blue.
Compare (def 18), (def 5), , .
/kwɑːk/
noun
1.
(physics) any of a set of six hypothetical elementary particles together with their antiparticles thought to be fundamental units of all baryons and mesons but unable to exist in isolation. The magnitude of their charge is either two thirds or one third of that of the electron
/kwɑːk/
noun
1.
a type of low-fat soft cheese
n.

1964, applied by U.S. physicist Murray Gell-Mann (b.1929), who said in correspondence with the editors of the OED in 1978 that he took it from a word in James Joyce’s “Finnegans Wake” (1939), but also that the sound of the word was in his head before he encountered the printed form in Joyce. German Quark “curds, rubbish” has been proposed as the ultimate inspiration [Barnhart; Gell-Mann’s parents were immigrants from Austria-Hungary]. George Zweig, Gell-Mann’s co-proposer of the theory, is said to have preferred the name ace for them.
quark
(kwôrk, kwärk)
Any of a group of elementary particles supposed to be the fundamental units that combine to make up the subatomic particles known as hadrons (baryons, such as neutrons and protons, and mesons). There are six different flavors (or types) of quark: up quark, down quark, top quark, bottom quark, charm quark, and strange quark. Quarks have fractional electric charges, such as 1/3 the charge of an electron. See Note at elementary particle. See Table at subatomic particle.
quarks [(kwahrks, kwawrks)]

In physics, the elementary particles that make up the protons and neutrons that in turn make up the atomic nucleus. Quarks are the most basic known constituent of matter. (See antimatter.)

Note: No quarks have been seen in the laboratory because, according to current theory, they cannot exist as free particles.