n.
- a minute portion of matter.
- Physics a subatomic constituent of the physical world, e.g. an electron, proton, neutrino, or photon.
- Grammar a minor function word that has comparatively little meaning and does not inflect, e.g. in, up, off, or over used with verbs to make phrasal verbs.
Etymology
ME: from L. particula ‘little part’, dimin. of pars, part-.