free radical

noun

: an especially reactive atom or group of atoms that has one or more unpaired electrons

especially : one that is produced in the body by natural biological processes or introduced from an outside source (such as tobacco smoke, toxins, or pollutants) and that can damage cells, proteins, and DNA by altering their chemical structure

Examples of free radical in a Sentence

Recent Examples on the Web

But when Böke peered inside dormant human and frog oocytes, they weren’t overloaded with free radicals at all. —Quanta Magazine, 13 May 2024

This work lends support to a longstanding theory that — because the chemical reaction underlying bioluminescence uses up oxygen — bioluminescence first evolved as a defense mechanism against the production of dangerous oxygen-containing molecules called free radicals. —Sam Jones, New York Times, 23 Apr. 2024

Word History

First Known Use

1870, in the meaning defined above

Medical Definition

free radical

noun

: an especially reactive atom or group of atoms that has one or more unpaired electrons

especially : one that is produced in the body by natural biological processes or introduced from outside (as in tobacco smoke, toxins, or pollutants) and that can damage cells, proteins, and DNA by altering their chemical structure