# radioactivity

/ˈɹeɪdioʊˌækˌtɪvəˌti/ (US) · /ɹˌeɪdɪəʊæktˈɪvɪti/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/radioactivity
Updated: 2026-05-19

## Definition

the process by which some materials give off energy and invisible rays. This happens because the atoms in these materials are unstable and change over time.

For teachers: the spontaneous emission of ionizing radiation from the nucleus of an atom, typically as a result of radioactive decay.

## Examples

- The scientist measured the radioactivity of the sample.
- The nuclear power plant is designed to safely manage the radioactivity produced by the fission of uranium atoms.
- While natural radioactivity is a constant background presence on Earth, the sudden increase in levels at the site raised significant concerns among the environmental monitoring team.

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