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

Other strengthening ingredients like collagen, peptides, fatty acids, and vitamin E can help plump, nourish, and protect hair from free radicals, which can encourage growth. —Ariel Wodarcyk, Glamour, 29 May 2026

Anthocyanins help fight free radicals and reduce inflammation.25 Beans are also an excellent source of protein and fiber, supporting weight management and helping to prevent type 2 diabetes.25 12. —Chelsea Rae Bourgeois, Health, 19 May 2026

Lowers Disease Risk Antioxidants are believed to protect against oxidative damage caused by exposure to free radicals. —Ross Phan, Verywell Health, 16 May 2026

These help to neutralize free radicals, which contribute to premature aging, pigmentation and collagen breakdown. —Leslie Baumann, Miami Herald, 7 May 2026

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