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

Chernobyl was the site of the 1986 disaster that spread radioactivity across parts of the Soviet Union and Europe. —Daria Tarasova-Markina, CNN, 14 Feb. 2025

On this day in 1898: Marie and Pierre Curie first isolated radium, research that led to them receiving half of a 1903 Nobel Prize for Physics along with Henri Becquerel, who discovered radioactivity in 1896. —Lorenzino Estrada, The Arizona Republic, 26 Dec. 2024

Inside, bright-yellow caution signs warned of radioactivity; photographs of lunar missions hung on the walls. —Dhruv Khullar, The New Yorker, 10 Feb. 2025

While a typical 28-gram serving of Brazil nuts contains 0.47 to 0.80 micro-sieverts, the maximum radioactivity found in a single mussel was 63.42 μSv. —Kevin Lynn, Newsweek, 7 Jan. 2025

Word History

Etymology

International Scientific Vocabulary

First Known Use

1899, in the meaning defined above

Rhymes for radioactivity

• bioactivity
• commutativity
• cooperativity
• generativity
• hyperactivity
• insensitivity
• interactivity
• overactivity
• performativity
• retroactivity
• absorptivity
• affectivity

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