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

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. — ABC News, 7 Sep. 2026

Sorghum is rich in protective plant compounds, such as polyphenols and other antioxidants, that help neutralize unstable molecules (free radicals) that can damage cells and promote inflammation over time. — Amy Brownstein, Verywell Health, 4 Sep. 2026

Moreover, the antioxidants in elderberries help protect the skin’s cells from things like free radicals that contribute to the intensity and duration of skin problems. — Bestreviews, Chicago Tribune, 4 Sep. 2026

Formulated with antioxidant vitamin E to help defend against surface free radicals, this product locks in moisture to hydrate the skin without leaving a greasy residue and dries completely matte upon application. — Alison Abbey Hudak, Footwear News, 1 Sep. 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