An amount of energy released during fusion and fission reactions is known as nuclear energy. When a heavy nucleus breaks into two nuclei and products of neutrons, energy is released, this energy is called nuclear energy. This process is called fission reaction. In fission reaction when a neutron falls on a nucleus, a heavy nucleus is formed which is unstable. In fusion reactions two nuclei are combined to form a heavy nucleus. This nucleus is more stable than the two nuclei. In the formation of this heavy nucleus an amount of energy is released, this energy is also a form of nuclear energy. The amount of the nuclear energy can be calculated by Einstein mass-energy equation. The formula for energy is delE=del m c2 ( 'del E' is the amount of energy released, 'del m' is the mass defect and c is the speed of light).
The meaning of nuclear energy is the power,usually electrical or motive power, produced by nuclear fission or fusion
This means every atomic nucleus contains energy that can be transformed into other forms of energy.
Its energy that holds nucleus of atoms together