radioactivity

noun

ra·​dio·​ac·​tiv·​i·​ty ˌrā-dē-ō-ak-ˈti-və-tē 

: the property possessed by some elements (such as uranium) or isotopes (such as carbon 14) of spontaneously emitting energetic particles (such as electrons or alpha particles) by the disintegration of their atomic nuclei

also : the rays emitted

Examples of radioactivity in a Sentence

Recent Examples on the Web

Physicists rely on them to unify the fundamental forces of nature: At high energies, group theory can be used to show that electromagnetism and the forces that hold atomic nuclei together and cause radioactivity are all manifestations of a single underlying force. —Leila Sloman, WIRED, 6 Oct. 2024

The double Nobel Prize winner is most famous for her discovery of radioactivity, as well as the radioactive elements radium and polonium. —Clara Moskowitz, Scientific American, 15 Oct. 2024

For instance, the Soviet government initially denied the catastrophic nuclear accident at Chernobyl in 1986 and admitted the magnitude of the disaster only when radioactivity measures skyrocketed in other countries. —Luis R. Martínez, Foreign Affairs, 10 May 2023

Europa Clipper will have to endure the level of radioactivity that would be produced by a thermonuclear war. —David W. Brown, The New Yorker, 15 Oct. 2024

Word History

Etymology

International Scientific Vocabulary

First Known Use

1899, in the meaning defined above

Kids Definition

radioactivity

noun

ra·​dio·​ac·​tiv·​i·​ty -ˌak-ˈtiv-ət-ē 

: the giving off of rays of energy or particles by the breaking apart of atoms of certain elements (as uranium)

Medical Definition

radioactivity

noun

ra·​dio·​ac·​tiv·​i·​ty -ak-ˈtiv-ət-ē 

plural radioactivities

: the property possessed by some elements (as uranium) or isotopes (as carbon 14) of spontaneously emitting energetic particles (as electrons or alpha particles) by the disintegration of their atomic nuclei