| Term | Definition |
| Alpha Particle | Weakest type of nuclear radiation; consists of a helium nucleus released during alpha decay. |
| Artificial Transmutation | Changing of one element into another by unnatural means; involves bombarding a nucleus with high-energy particles to cause change. |
| Gamma Ray | High-frequency electromagnetic wave released during gamma decay; strongest type of nuclear radiation. |
| Beta Particle | Electron, created in the nucleus of an atom, released during beta decay. |
| Binding Energy | Energy associated with the strong nuclear force that holds an atomic nucleus together, related to the stability of a nucleus. |
| Decay Series | Sequence of steps by which a radioactive nucleus decays into a non-radioactive nucleus. |
| Half-Life | Amount of time it takes for half the atoms in a given sample of an element to decay. |
| Radioactive Decay | Process in which a nucleus spontaneously emits particles or rays to become lighter and more stable. |
| Radioactivity | Release of energy and matter that results from changes in the nucleus of an atom. |
| Tracer | Radioactive element whose pathway can be followed through the steps of a chemical reaction or industrial process. |
| Transmutation | Process in which one element is changed into another as a result of changes in the nucleus. |
| Critical Mass | The smallest mass of a fissionable material that will sustain a nuclear chain reaction at a constant level. |
| Nuclear Chain Reaction | Series of fission reactions that occur because the products released during one fission reaction cause the fission reactions in other atoms. |
| Nuclear Fission | Splitting of an atomic nucleus into two smaller nuclei of approximately equal mass. |
| Nuclear Fusion | Joining of two atomic nuclei of smaller mass to form a single nucleus of larger mass. |
| Transuranium Element | Element formed synthetically; has more than 92 protons in its nucleus. |
| Nuclear Reactor | Any of several devices in which a chain reaction is initiated and controlled, with the resulting heat typically used for power generation and the neutrons and fission products used for military, experimental, and medical purposes. |
