Main Entry: pro·ton

Pronunciation: \ˈprō-ˌtän\

Function: noun

Etymology: Greek prōton, neuter of prōtos first — more at prot-

Date: 1920

: an elementary particle that is identical with the nucleus of the hydrogen atom, that along with the neutron is a constituent of all other atomic nuclei, that carries a positive charge numerically equal to the charge of an electron, and that has a mass of 1.673 × 10⁻²⁷ kilogram

— pro·ton·ic \prō-ˈtä-nik\ adjective