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

Alongside these minerals, dark chocolate is rich in antioxidants, which help counteract free radicals—harmful molecules linked to chronic diseases. —Lana Barhum, Verywell Health, 13 Apr. 2026

Moreover, honey is rich in antioxidants, which thwart skin-aging free radicals in the environment. —Sophie Wirt, InStyle, 9 Apr. 2026

Better Heart Health Green tea contains antioxidants like polyphenols and catechins, which reduce harmful compounds called free radicals in the body. —Trista Chan, Health, 8 Apr. 2026

This face serum brightens and evens skin tone, fights free radicals, supports collagen production, and softens the look of fine lines and wrinkles for glowing, healthy-looking skin. —Tory Johnson, ABC News, 28 Mar. 2026

Word History

First Known Use

1870, in the meaning defined above

Rhymes for free radical

• radicle

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