The weak interaction, also known as the weak nuclear force, is one of the four fundamental forces in nature. It is responsible for processes like radioactive decay and the fusion of particles in stars. This force operates at a very short range, typically less than the size of an atomic nucleus, and is crucial for the stability of matter. In particle physics, the weak interaction involves the exchange of particles called W and Z bosons. These bosons mediate the force between quarks and leptons, leading to transformations such as the conversion of a neutron into a proton. This interaction plays a vital role in the processes that power the sun and other stars.