In particle physics, a hadron (pronounced /?hadr?n/, from the Greek: ?δρ??, hadros, “stout, thick”) is a composite particle made of quarks held together by the strong force (similarly to how atoms and molecules are held together by the electromagnetic force). Hadrons are categorized into two families: baryons (made of three quarks), and mesons (made of one quark and one antiquark).
Note that the mass of a hadron has very little to do with the mass of its valence quarks; rather, due to mass–energy equivalence, most of the mass comes from the large amount of energy associated with the strong interaction.
— Wikipedia on Hadron
2010.07.22 Thursday ACHK