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

Editor’s tip: This primer’s purple tea extract is packed with powerful antioxidants that help fight off free radicals and shield your lips from environmental stressors. —Christa Joanna Lee, Allure, 2 Mar. 2025

This formulation blends hydrating baobab seed oil with antioxidant-rich hibiscus flower extract and desert date oil to protect against free radical damage and reduce the appearance of fine lines. —Conçetta Ciarlo, Vogue, 27 Feb. 2025

Infused with 12-hour time-release vitamin C, this formula also features Japanese plum and ferulic acid to help protect your skin from free radical damage. —Denise Primbet, Glamour, 21 Feb. 2025

May Reduce Inflammation Soybeans are high in antioxidants, which help eliminate harmful compounds called free radicals. —Merve Ceylan, Health, 20 Feb. 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