Radioactivity

Part of speech: noun

Pronunciation: /ˌreɪdɪəʊakˈtɪvɪti/

Definitions

1. The emission of energy and particles from unstable atomic nuclei as they spontaneously decay into more stable forms
2. The spontaneous release of energy and subatomic particles from unstable atoms as their nuclei transform toward stability
3. Unstable atomic nuclei's natural tendency to emit radiation and particles while undergoing decay into more stable elements

Etymology: Henri Becquerel's 1896 discovery that uranium salts fogged photographic plates in the dark is the event behind this word, though the word itself came later. Marie Curie coined "radioactivity" to name the phenomenon she studied in uranium and thorium, building it from "radio-", a combining form from Latin "radius" meaning ray, and "activity," the ordinary English noun for action or operation. The result describes a property of matter rather than a process of light or heat. The compound is a straightforward piece of scientific coinage, not a classical inheritance. Ancient writers had no concept of spontaneous nuclear decay, so the word's classical elements were simply recombined to name a new discovery. Some dictionaries also treat it as derived from the adjective "radioactive" plus the suffix "-ity," which is the same process applied to a different base.

Synonyms: radiation, activity, nuclear activity, radioisotopes, radiological

Antonyms: stability, inactivity, non-radioactivity, quiescence, calmness