What defines the radiation emitted as a result of materials attempting to reach stability?

Decay is the process that defines the radiation emitted by unstable atomic nuclei as they attempt to reach a more stable state. When certain isotopes have an imbalance in the number of protons and neutrons, they undergo radioactive decay, emitting energy in the form of particles or electromagnetic radiation in the process. This emission occurs as the nucleus transforms, eventually leading to a more stable configuration.

Contamination refers to the presence of radioactive material in unwanted locations or on surfaces, which does not inherently relate to the stability of the materials themselves. Radiation is a broader term that refers to the energy emitted in various forms, including particles and waves, but does not specifically describe the process of reaching stability through decay. Ionization, on the other hand, is a result of radiation interacting with matter, leading to the removal of electrons from atoms, but it does not define the process through which unstable materials emit radiation to become stable.

Thus, decay appropriately encapsulates the concept of materials emitting radiation in their quest for stability.