proton - (n.)

A positively charged elementary particle of mass equal to that of a neutron and almost two thousand times that of an electron; a component, with neutrons, of all atomic nuclei : The nucleus of the hydrogen atom : A hydrogen ion, H*, arising either through the removal of the peripheral electron from a hydrogen atom or, together with a hydroxyl ion, from the dissociation of a water molecule. ~ See Also: Electron, Hydroxyl ion, Isotopes, Neutron, Nucleus.