An Etymological Dictionary of Astronomy and Astrophysics

In particle physics, a constituent of the hadron originally postulated in the theoretical analysis of high-energy scattering of particles off hadrons. In modern usage, the term parton is often used to mean a quark or a gluon.

See also: Coined by the American physicist Richard Feynman (1918-1988), from part, from → particle + → -ion