Why are fission and fusion called nuclear energy?

Answer 1

Nuclear energy is the source of the energy produced by both fission and fusion. Per Einstein's equation E = mc2 matter may be converted into energy. In fission, the nuclei of heavy atoms like Uranium or Plutonium are split into less heavy elements. Byproducts of fission are nuclear energy and neutrons that may be used to sustain the nuclear fission process as in a reactor or a bomb. In fusion, two nuclei are merged (or fused) to form a heavier element. Often two Hydrogen atoms are fused to form a Helium atom. Fusion is the process that occurs in our sun. Both fission and fusion result in the conversion of a small amount of the matter in the nuclei of the source atom(s) into energy. Therefore, both may be considered nuclear energy.