Nuclear fusion is a reaction through which two or more light nuclei collide to form a heavier nucleus. The nuclear fusion process occurs in elements that have a low atomic number, such as hydrogen. Nuclear Fusion is the opposite of nuclear fission reaction in which heavy elements diffuse and form lighter elements. Both nuclear fusion and fission produce a massive amount of energy.
Nuclear Fusion Definition:
Nuclear fusion is when two or more atomic nuclei fuse to form a single heavier nucleus. In the reaction, the matter is not conserved because some of the mass of the fusing nuclei is converted to energy.