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

Example Sentences

Recent Examples on the Web

Tests showed 35 employees absorbed elevated levels of radioactivity, though most showed a dose akin to a chest X-ray, the department found. —Daniel Moore, Chicago Tribune, 7 May 2023

The radioactivity is limited, so several rounds of treatment are usually needed to tackle the cancer. —Calum Chace, Forbes, 21 Apr. 2023

Partners in life and in science, the couple’s fruitful work together produced the discovery of the elements polonium and radium in 1898, as well as radioactivity itself. —Stephen C. George, Discover Magazine, 14 Feb. 2023

Other instruments expected to start operating around the same timeframe include a gamma-ray spectrometer for monitoring radioactivity levels and a single-photon stereo camera to measure bioluminescence of deep-sea organisms. —Dhananjay Khadilkar, Ars Technica, 31 Mar. 2023

Caesium-137 has a half-life of about 30 years, which means that after three decades, the capsule’s radioactivity would halve, and after 60 years would halve again, meaning the lost capsule could have remained radioactive for as long as 300 years. —Hilary Whiteman, CNN, 1 Feb. 2023

While the government estimates relied mostly on data from monitoring stations in Japan, the European research team behind the new report looked at radioactivity data from stations scattered across the globe. —Valerie Ross, Discover Magazine, 28 Oct. 2011

Marie Curie was a Polish scientist who discovered both polonium and radium, and coined the term radioactivity. —Rebecca Norris, Woman's Day, 27 Jan. 2023

Members of the public can suggest sites that should be tested, collect data on radioactivity, and raise funds to cover the cost of the research. —Eva Lewandowski, Discover Magazine, 8 June 2016

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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