free radical

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noun Chemistry, Biochemistry.

an atom or molecule that bears an unpaired electron and is extremely reactive, capable of engaging in rapid chain reactions that destabilize other molecules and generate many more free radicals: in the body, deactivated by antioxidants, uric acid, and certain enzyme activities.

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Compare diradical.

Origin of free radical

First recorded in 1895–1900

Words nearby free radical

freephone, free port, Freepost, free press, freer, free radical, free-range, free-range parenting, free reach, free reaching, free recall

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022

How to use free radical in a sentence

Long-term users didn’t show a big increase in free radicals when they vaped.
A single vape session can harm immune cells in the body|Alison Pearce Stevens|October 15, 2021|Science News For Students
Mohara explains that free radicals in polluted air touch your skin and trigger a chemical reaction that destroys collagen.
7 things you can do to actually prevent wrinkles|Sandra Gutierrez|July 13, 2021|Popular-Science
This compound has several functions, including fighting free radicals that may be slowing down your collagen production, boosting the production of new collagen, and helping you safely store the collagen you already have.
7 things you can do to actually prevent wrinkles|Sandra Gutierrez|July 13, 2021|Popular-Science
In other words, the free thinker defending freedom of thought.
Houellebecq’s Incendiary Novel Imagines France With a Muslim President|Pierre Assouline|January 9, 2015|DAILY BEAST

Tend to your own garden, to quote the great sage of free speech, Voltaire, and invite people to follow your example.
How the PC Police Threaten Free Speech|Nick Gillespie|January 9, 2015|DAILY BEAST
The simple, awful truth is that free speech has never been particularly popular in America.
How the PC Police Threaten Free Speech|Nick Gillespie|January 9, 2015|DAILY BEAST
Cambodia, with its seemingly free press, is also a haven for foreign journalists.
Cambodia’s Smoke-and-Mirrors Democracy|David Shaftel|January 9, 2015|DAILY BEAST
In other words, the free speech exhibited by the folks at Charlie Hebdo was not virtuous—until there was a body count.
Politicians Only Love Journalists When They're Dead|Luke O’Neil|January 8, 2015|DAILY BEAST
What need to look to right or left when you are swallowing up free mile after mile of dizzying road?
The Joyous Adventures of Aristide Pujol|William J. Locke
It seemed to free her of a responsibility which she had blindly assumed and for which Fate had not fitted her.
The Awakening and Selected Short Stories|Kate Chopin
If we can free this State of Yankees, we will accomplish more than your armies down south have.
The Courier of the Ozarks|Byron A. Dunn
The voice of the orator peculiarly should be free from studied effects, and responsive to motive.
Expressive Voice Culture|Jessie Eldridge Southwick
Above all, he was amazed to hear me talk of a mercenary standing army in the midst of peace and among a free people.
Gulliver's Travels|Jonathan Swift

British Dictionary definitions for free radical

free radical

noun

an atom or group of atoms containing at least one unpaired electron and existing for a brief period of time before reacting to produce a stable moleculeSometimes shortened to: radical Compare group (def. 10)

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for free radical

free radical

An uncharged atom or group of atoms having at least one unpaired electron, which makes it highly reactive.

An organic compound having some unpaired valence electrons; a normal byproduct of oxidation reactions in metabolism.

Scientific definitions for free radical

free radical

An atom or group of atoms that has at least one unpaired electron and is therefore unstable and highly reactive. In animal tissues, free radicals can damage cells and are believed to accelerate the progression of cancer, cardiovascular disease, and age-related diseases.