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

Excessive free radicals can cause oxidative stress, which damages cells and other materials in the body, such as DNA. —Melissa Nieves, Verywell Health, 1 May 2025

It’s boosted by vitamins C and E as well as ferulic acid to help protect the skin from free radicals and bring your dull complexion back to life with its superb brightening benefits. —Denise Primbet, Glamour, 28 Apr. 2025

In particular, smoking, vaping, drinking alcohol, skipping sleep, using recreational drugs (like marijuana), and downing a ton of sugar may all contribute to an excess of those free-wheeling free radicals and impair your body’s ability to defend against them. —Erica Sloan, SELF, 18 Apr. 2025

Such benefits are most commonly associated with ginkgo's high concentration of a type of antioxidant known as flavonoids — which are known to neutralize damage related to free radicals. —Daryl Austin, USA Today, 15 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