Dear PF Forum, Can proton be annihilated by anti neutron? Can proton be annihilated by positron? Can neutron be annihilated by positron? Does every particle has to match its antiparticle to be annihilated, example: Proton must be annihilated by anti-proton, not by anti neutron. I've heard that there's anti neutrino, too. Does every particle fundamental also, such as quark, have coresponding anti particle? Are there particles that have no antiparticle? Thanks for the answer. I know, should have searched google, but to find this particular answer takes every long time.