• Type of subatomic particle (several different quarks are known) which form the ‘building blocks’ of protons, neutrons and other nuclear particles
  • An elementary particle, with a fractional charge of 1/3 or 2/3, combinations of which are considered to constitute all hadrons. So far six types of quarks have been identified, and a proton, for instance, consists of two up quarks and a down quark. A quark and antiquark pair form a meson. So far, an isolated quark has not been observed.

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