- a meson with strangeness +1 and either positive or zero electric charge, or its antiparticle, with strangeness −1 and either negative or zero electric charge. Symbol: K
- another name for kaon
- a meson that has a positive or negative charge and a rest mass of about 966 electron masses, or no charge and a rest mass of 974 electron massesAlso called: K-meson
- See kaon.
- Any of three unstable mesons, one having charge +1 and a mass of 966 electron masses, and two being electrically neutral, with a mass 974 electron masses. Their half-life is approximately 10-8 seconds, and they decay through the weak force. Their decay patterns suggest that CP invariance may be violated. Also called K-meson K particle See Table at subatomic particle.