Any of a class of subatomic particles composed of a combination of two or more quarks or antiquarks. Quarks (and antiquarks) of different colors are held together in hadrons by the strong nuclear force. Hadrons include both baryons (composed of three quarks or three antiquarks) and mesons (composed of a quark and an antiquark). The combination of quark colors in a hadron must be neutral, for example, red and antired (as in a pion) or red, blue, and green (as in a proton). Compare baryon, lepton.