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

What Happens to the Body During Earthing The electrons absorbed through skin contact are thought to act as natural antioxidants, neutralizing free radicals — unstable molecules that contribute to cellular inflammation and tissue damage. —Allison Palmer, Fort Worth Star-Telegram, 21 Apr. 2026

The fruit is also a great source of beta-carotene, which works to protect one's body from damaging molecules called free radicals. —Daryl Austin, USA Today, 18 Apr. 2026

Extra virgin olive oil is also a good source of vitamin E, an antioxidant that can help neutralize free radicals to prevent oxidative damage to cells. —Isabel Vasquez Rd Ldn, Health, 16 Apr. 2026

Alongside these minerals, dark chocolate is rich in antioxidants, which help counteract free radicals—harmful molecules linked to chronic diseases. —Lana Barhum, Verywell Health, 13 Apr. 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