weak interactions, actions between elementary particles mediated, or carried, by W and Z particles and that are responsible for nuclear decay. Weak interactions are one of four fundamental interactions in nature, the others being gravitation, electromagnetism, and the strong interactions.

strong interactions, actions between elementary particles mediated, or carried, by gluons. They are responsible for the binding of protons and neutrons in the nucleus and interactions between quarks. Quantum field theory applied to the understanding of these strong interactions is called quantum chromodynamics (QCD). Strong interactions are one of four fundamental interactions in nature, the others being gravitation, electromagnetism, and the weak interactions.