[ ree-ak-shuh n ]
/ riˈæk ʃən /


Origin of reaction

1635–45; re- + action, modeled on react

Related forms Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for counter-reaction

  • Nevertheless, a counter-reaction was created, to which England owes her great reforms of the nineteenth century.

  • It had arisen partly from this cause, that there had been something of a counter-reaction at the last general election.

    The Duke's Children|Anthony Trollope

British Dictionary definitions for counter-reaction


/ (rɪˈækʃən) /


Derived Forms

reactional, adjective


Reaction is used to refer both to an instant response (her reaction was one of amazement) and to a considered response in the form of a statement (the Minister gave his reaction to the court's decision). Some people think this second use is incorrect
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 counter-reaction


[ rē-ăkshən ]


A response of an organism or living tissue to a stimulus.
The state resulting from such a response.
A chemical change or transformation in which a substance decomposes, combines with other substances, or interchanges constituents with other substances.
The response of cells or tissues to an antigen, as in a test for immunization.
A pattern of behavior constituting a mental disorder or personality type.

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for counter-reaction


[ rē-ăkshən ]

A rearrangement of the atoms or molecules of two or more substances that come into contact with each other, resulting in the formation of one or more new substances. Chemical reactions are caused by electrons of one substance interacting with those of another. The reaction of an acid with a base, for example, results in the creation of a salt and water. Some, but not all, reactions can be reversed.
See nuclear reaction.
An action that results directly from or counteracts another action, especially the change in a body's motion as a result of a force applied to it. Some reactions counteract forces and are not readily apparent. When an object rests on a surface, such as a table, for example, the downward force it applies to the surface is counteracted by an equal but upwards force, or reaction, applied by the surface. See more at Newton's laws of motion.
A response to a stimulus, such as a reflex.
The response of cells or tissues to an antigen, as in a test for immunization.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.