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

Is High in Antioxidants Orange juice is rich in healthy nutrients called antioxidants, compounds that help prevent cell damage from unstable molecules called free radical damage in a process known as oxidative stress. —Aviv Joshua, Ms, Verywell Health, 11 Feb. 2025

Antioxidants in blueberries help combat free radicals, reducing cellular damage and potentially slowing brain aging in senior dogs. —Justin Gest, Newsweek, 10 Feb. 2025

Mitochondria normally neutralize free radicals, but, when radiation injures them, this process becomes more difficult; the free radicals then damage mitochondrial DNA, and that weakens the mitochondria further. —Dhruv Khullar, The New Yorker, 10 Feb. 2025

Many doctors recommend glutathione to their patients for its ability to break down free radicals and detoxify the body. —Elycia Rubin, The Hollywood Reporter, 7 Feb. 2025

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