Nuclear fusion is a process whereby the nuclei of two smaller atoms combine to form a much larger atom, accompanied with the release of energy. This is opposed to nuclear fission where a larger atom splits into simpler and smaller atoms.
According to this question, the process of releasing energy when two stoms combine to form a larger atom is called NUCLEAR FUSION. A very common example of nuclear fusion is the combination of hydrogen atoms in the sun to produce Helium atom, with the release of heat energy.
