The energy producing nuclear interaction of light elements requires some clarification. Frequently, all light element energy-producing nuclear interactions are classified as fusion, however by the given definition above fusion requires that the products include a nucleus that is heavier than the reactants. Light elements can experience energy producing nuclear interactions by fusion or fission. All energy producing nuclear interactions between two Hydrogen isotopes and between hydrogen and helium-3 are fusion as the product of these interactions include a heavier nucleus. However, the energy producing nuclear interaction of a neutron with Lithium–6 produces Hydrogen-3 and Helium-4, each a lighter nucleus. By the definition above, this nuclear interaction is fission, not fusion. When fission is caused by a neutron, as in this case, it is called induced fission.