Hadrons

The name “Hadron” comes from the Greek for “stout” or “thick.” They are subatomic composite particles. They are made of two or more quarks held together by the strong nuclear force. This is similar to the way molecules are held together by the electromagnetic force. The majority of the mass in ordinary matter comes from two hadrons: the proton and the neutron. 

There are two families of hadrons: baryons, which have an odd number of quarks, usually three, and mesons, which are made of an even number of quarks, usually one quark and one antiquark. The majority of the mass of the atom is contained in the protons and neutrons. Protons and neutrons are examples of baryons. Pions are an example of a meson. There have been exotic hadrons discovered in recent years.