# radon

/ˈɹeɪˌdɑn/ (US) · /ɹˈeɪdɒn/ (UK) · CEFR C1 · Noun

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

## Definition

a gas that comes from the natural breakdown of uranium in rocks and soil. It is invisible and can be dangerous if it builds up inside homes.

For teachers: a radioactive noble gas produced by the decay of radium, which itself is a decay product of uranium. It is colourless, odourless, and chemically inert, but poses a significant health risk when inhaled in high concentrations.

## Examples

- Radon levels in the basement are too high for safety.
- The health department recommends testing for radon in every new home to prevent long-term exposure to the gas.
- While radon is a naturally occurring element, its accumulation in poorly ventilated structures can lead to lung cancer, making it the second leading cause of the disease after smoking.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.