free radical

noun

Definition of free radical

: 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

Recent Examples of free radical from the Web

Antioxidant Cures Whitney Bowe, a clinical assistant professor of dermatology at the Icahn School of Medicine at Mount Sinai Medical Center in New York City, and author of The Beauty of Dirty Skin, researches free radicals and acne.

— jolene edgar, Allure, "Experts Predict What the Future of Fillers, Lasers, and Injectables Will Look Like," 26 Oct. 2017
Look to Antioxidants for Help The body only has so many lines of defense in the fight against free radicals, which include wrinkle- and sag-inducing molecules generated by UV exposure.

— chloe atkins, Vogue, "4 Dermatologist-Approved Ways to Reverse Summer Skin Damage," 4 Sep. 2017
The free radicals can act as signaling molecules, stimulating the epidermis to regenerate.

— jolene edgar, Allure, "The Antioxidant Debate: Experts Weigh In On Whether or Not They're Harmful to Your Skin," 3 Nov. 2017
Reactive oxygen species, or free radicals, are a type of unstable molecule that contains oxygen and easily reacts with other molecules.

— susan scutti, CNN, "Exposure to air pollution before birth may shorten our lives," 16 Oct. 2017
The gel cleanser, made with soothing shea butter and free radical-fighting grapeseed oil, scrapes away the most stubborn of waterproof mascaras, leaving skin feeling fresh and clean — but never stripped.

— sarah kinonen, Allure, "6 Skin-Care Products From Sephora I'm Loving Right Now," 3 Oct. 2017
Within cells, a buildup of these free radicals may cause damage to DNA, RNA and proteins, which could eventually lead to cell death and so too cardiovascular disease.

— susan scutti, CNN, "Exposure to air pollution before birth may shorten our lives," 16 Oct. 2017
This activates free radicals that contain toxins, which greatly accelerates the process of aging, as well as damages the skin's barrier and elasticity, causing inflammation.

— lauren valenti, Marie Claire, "The Beauty Girl's Guide to Fighting Off Pollution," 28 May 2015

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'free radical.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of free radical

1870

Medical Dictionary

free radical

noun

medical Definition of free radical

: 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