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

Researchers need to design new materials that can decay within a few years to levels of radioactivity that can be disposed of safely and more easily. —Farhat Beg, The Conversation, 8 Jan. 2025

The study also compared the mussels' radioactivity to Brazil nuts, which naturally absorb radiation from the soil. —Kevin Lynn, Newsweek, 7 Jan. 2025

Within 40 years the radioactivity is reduced to one-thousandth of when the fuel was unloaded, and within 1,000 to 10,000 years the fuel is only as radioactive as the original ore it was made from. —David Szondy, New Atlas, 28 Dec. 2024

Photons transmit the electromagnetic force; gluons hold particles together in the atomic nucleus; and W and Z particles transmit the weak nuclear force, important for some forms of radioactivity. —Tom Siegfried, Discover Magazine, 29 Nov. 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