11.2.4—A hadron may be either a baryon (consisting of three quarks) or a meson

Baryons are three-quark states such as protons and neutrons; mesons are quark–antiquark states. Both are hadrons and feel the strong interaction.

Check quark and antiquark charges when classifying a particle, and remember that the simple composition labels do not determine stability alone.

A proton is a baryon uud, while a pion is a meson made from a quark and an antiquark combination.

Leptons are not hadrons, and a meson is not “two baryons”; it contains one quark and one antiquark.