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

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The antioxidant also protects your cells against the damaging effects of free radicals and aids in the absorption and storage of iron. — Caroline Picard, Good Housekeeping, "4 Surprising Health Benefits of Chestnuts," 13 Dec. 2018 Sid was being fueled by free drugs, so that’s the free radical gone in him. — Corey Seymour, Vogue, "Johny Lydon On the Sex Pistols, Crashing The Met Ball—And A New Documentary, The Public Image Is Rotten," 13 Sep. 2018 La Prairie’s Skin Caviar Luxe Cream has been a bestseller since the late ’90s, thanks to firming and free radical–fighting marine extracts, but the brand’s new incarnation has been updated with cutting-edge technology for extra support this season. — Jenna Rennert, Vogue, "10 Face Creams to Combat Winter Skin Before It Starts," 13 Oct. 2018 The Ageless Enriching Renewal Cream is rich in free radical-fighting antioxidants and hydrating hyaluronic acid to reduce the loss of elasticity and dullness in the face. — Tanisha Pina, Allure, "Tatcha's Labor Day Sale Features Major Deals on All These Skin-Care Products," 30 Aug. 2018 If left unchecked, chronic inflammation can lead to signs of skin aging by creating free radicals that scavenge electrons from healthy cells, therefore rendering them unstable. — Dr. Leslie Baumann, miamiherald, "Improving your diet can also improve your skin | Miami Herald," 22 Jan. 2018 Much like the sun causes skin cancer, the damage from UV rays can cause the creation of destructive molecules within the body, called free radicals, Khan explains. — Macaela Mackenzie, Allure, "The Scary Way Blue Light From Your Phone Can Affect Your Eyes and Vision," 6 July 2018 Research published in the Journal of Nutrition found that a zinc deficiency in rats led to impairments in DNA repair caused by free radicals, which can speed the aging process. — Amy Capetta, Woman's Day, "5 Anti-Aging Supplements That May Actually Work," 16 Oct. 2018 Like other berries, açaí are packed with antioxidants that can help build up your immune system and protect your cells against damage from free radicals. — Tehrene Firman, Good Housekeeping, "10 Things You Should Know About Açaí Berries, Nature's "Purple Gold"," 23 July 2018

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.

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The first known use of free radical was in 1870

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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