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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Antioxidants neutralize destructive compounds in cells called free radicals, which can cause cell damage and promote inflammation, which can lead to cardiovascular disease. Kathi Valeii Published, Verywell Health, 8 Oct. 2025 These help prevent oxidation, chemical reactions that produce free radicals (substances that damage cells and contribute to chronic disease). Mark Gurarie, Health, 30 Sep. 2025 And with a boost of antioxidants from La Roche-Posay’s signature thermal spring water, the face serum makes skin more resilient, protecting it from free radicals and environmental aggressors alike. Danielle Cohen, Glamour, 18 Sep. 2025 This lightweight, silky formula pairs broad-spectrum sun protection with antioxidant-rich white tea to help fend off free radicals and environmental stressors that can accelerate visible aging. Christa Joanna Lee, Allure, 12 Sep. 2025 See All Example Sentences for free radical

Word History

First Known Use

1870, in the meaning defined above

Time Traveler
The first known use of free radical was in 1870

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Cite this Entry

“Free radical.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/free%20radical. Accessed 19 Oct. 2025.

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

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