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

Antioxidants neutralize free radicals by donating electrons to stabilize reactive molecules without becoming harmful themselves, thereby halting oxidative damage and protecting cells and tissues. —Lana Barhum, Verywell Health, 13 May 2026

These help to neutralize free radicals, which contribute to premature aging, pigmentation and collagen breakdown. —Leslie Baumann, Miami Herald, 7 May 2026

Why Antioxidants May Be Able To Help Prevent Skin Cancer UV rays can cause the body to produce too many free radicals, which are molecules that can damage DNA and other crucial cell parts. —Carrie Madormo, Health, 5 May 2026

Argan oil is rich in antioxidants, which protect hair from free radical damage. —Bestreviews, Mercury News, 4 May 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