[{"Bold_text": "noun", "List Items": ["a particle of whose properties, as mass, spin, or charge, have the same magnitude as but, where appropriate, the opposite sign of a specific elementary particle elementary particle;neutral pions, photons, and gravitons are considered to be their own antiparticles:Compare antimatter , annihilation(def3) annihilation(def3).The positron is the antiparticle of the electron."]}]