- a proton, neutron, or any elementary particle that decays into a set of particles that includes a proton.
- any of a class of elementary particles that have a mass greater than or equal to that of the proton, participate in strong interactions, and have a spin of 1/2 . Baryons are either nucleons or hyperons. The baryon number is the number of baryons in a system minus the number of antibaryons
