Radioactivity: The emission of ionizing radiation or particles caused by decay or disintegration of atomic nuclei. Both uranium and plutonium are radioactive.
Nuclear Fission: A reaction in which a nucleus is split into two smaller parts, releasing a large amount of energy. This process powers both nuclear reactors and bombs using uranium or plutonium.
Nuclear Reactor: A device used to initiate and control a self-sustained nuclear chain reaction, typically for generating electricity or for propulsion in submarines. They use uranium or plutonium as fuel.