Radionuclide

Part of speech: noun

Definitions

1. A substance that releases radiation owing to the transformation of its atomic nuclei
2. A material identified by the property of emitting radiation due to the instability of its atomic nucleus resulting in decay events
3. An atom or element that emits radiation due to an unstable nucleus undergoing decay

Etymology: "Radionuclide" is a plain technical compound, built from "radio-" and "nuclide." The first part traces back to the Latin "radius," meaning a ray or spoke of a wheel, and it reached English as a combining element used to name things connected with radiation. The second part, "nuclide," is a term for a species of atom defined by the number of protons and neutrons in its nucleus, so the whole word names a nuclide that is radioactive, meaning its nucleus decays and gives off radiation. Because the word is assembled from two existing scientific building blocks rather than inherited through everyday speech, its history is essentially the history of those parts. Its meaning is precise: it refers to the unstable nuclide itself, not to radiation as a general phenomenon.

Synonyms: radioisotope, radiochemical