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DictionaryradioactiveEmitting radiation
adjective

radioactive

ray-dee-oh-AK-tiv/ˌreɪdiəʊˈæktɪv/

Emitting ionizing radiation through atomic decay.

The radioactive nucleus releases an alpha particle and a gamma ray.

A text-free scientific visualization of radioactive decay: a compact atomic nucleus releases an alpha particle and a gamma ray, making nuclear emission rather than broadcasting the central subject.
Etymology
radioLatinray
+activeFrenchactive

“Ray” and “active” describe activity that releases radiation. In this nuclear sense, the activity is spontaneous decay of an unstable nucleus, which releases ionizing emissions.

In context

Theories Demystified0:32
discovered radioactivity comes from within an atom's nucleus a revolutionary idea at the time she found radioactive elements constantly emit energy breaking down into other elements
Radium, Polonium & Radioactivity: Marie Curie's Discoveries

More examples

  • Some rocks contain small amounts of radioactive uranium.
  • Workers store radioactive waste in specially designed containers.
  • Doctors use radioactive iodine to treat certain thyroid conditions.

Forms

radioactive

radioactivity noun — The emission of radiation through atomic decay.

Similar words

radiating
Includes giving off heat or light without atomic decay.
hot
Informally means radioactive, especially when describing contaminated objects or areas.