The fundamental force that acts between leptons and is involved in the decay of hadrons. The weak nuclear force is responsible for nuclear beta decay (by changing the flavor of quarks) and for neutrino absorption and emission. It is mediated by the intermediate vector bosons (the W boson and the Z boson), and is weaker than the strong nuclear force and the electromagnetic force but stronger than gravity. Some scientists believe that the weak nuclear force and the electromagnetic force are both aspects of a single force called the electroweak force. Also called weak nuclear force, weak interaction. Compare electromagnetic force.