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

The antioxidant ingredient can also help to protect the skin against free radical damage and wrinkles according to a study. —Rosa Jisoo Pyo, Vogue, 28 Mar. 2025

So while oxidation can be good, Zamora added, peroxidation is a process in which unstable molecules known as free radicals attack fats containing double bonds. —Kristen Rogers, CNN, 25 Mar. 2025

Antioxidants protect cells from damage caused by free radicals. —Emily Kay Votruba, EverydayHealth.com, 12 Mar. 2025

Cold water can increase blood flow to your face, boosting your skin's protection from free radicals, harmful compounds caused by exposure to UV light and pollution. —Sherri Gordon, Health, 6 Mar. 2025

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