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 counter destructive free radical molecules in cells, acting to reduce inflammation and the risk of chronic disease. —Angelica Bottaro, Verywell Health, 23 July 2025

Studies show that beet juice can protect the liver from free radical damage and oxidative stress. —Audrey Noble, Vogue, 21 July 2025

Smalls sells a serum called To the Root that aims to neutralize free radicals from sun exposure and deliver antioxidants to encourage growth. —Jessica Hartshorn, Flow Space, 18 July 2025

The best vitamin C cleansers can come in handy for this—most are packed with brightening antioxidants and fruit enzymes to gently slough away dull, dead skin and protect it from free radicals. —Alanna Martine Kilkeary, Glamour, 17 July 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