Physics particles are subatomic particles that make up matter. An ION is an electrically charged ATOM or molecule, a meson is a type of hadron particle composed of a QUARK and an antiquark, a QUARK is a type of elementary particle, an OMEGA is a baryon composed of three quarks, a muon is an elementary particle similar to the electron, a positron is the antiparticle of the electron, a pion is a meson composed of a QUARK and an antiquark, a boson is a type of particle with integer spin, an ATOM is the smallest unit of matter, and a TAU is an elementary particle similar to the electron.