Radon (noun)

A naturally occurring radioactive gas of the noble gas series, present in small amounts in the atmosphere but becoming concentrated in enclosed spaces such as mines and buildings.

Origin:

Early 20th century: from r(adium) + -on.

Examples:

1. The house had a high level of radon and was deemed unsafe.
2. Radon is the leading cause of lung cancer among non-smokers.
3. The radon levels in the basement were tested by a professional.
4. Radon gas is invisible and odorless, making it difficult to detect.
5. Radon is a naturally occurring element, but in high concentrations it can be harmful to health.