free radical
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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Nearby words
free on board, free on rail, free perspective, free port, free press, free radical, free reach, free reaching, free recall, free rein, free ride
Compare diradical.
Origin of free radical
First recorded in 1895–1900
Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
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
Medicine definitions for free radical
free radical
n.
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.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Science 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.
The American Heritage® Science Dictionary
Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.