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

This antioxidant trio will help brighten dark spots and protect the skin from free radicals too. —Kristin Canning, SELF, 8 May 2025

Some studies indicate turmeric may help by lowering oxidative stress (an imbalance between harmful molecules called free radicals and helpful antioxidants that can cause cell damage) and supporting healthier vessel structure. —Patricia Weiser, Pharmd, Verywell Health, 29 Apr. 2025

Women in the late-onset menopause group also had better mitochondria function, meaning fewer free radicals and less oxidative stress. —Elizabeth Yuko, Health, 19 Apr. 2025

It should also be noted that this isn't a reason to forgo sunscreen, which is needed to protect from free radicals and prevent skin cancer. —Mélanie Defouilloy, Vogue, 14 Apr. 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