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reaction - 10 dictionary results
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re⋅ac⋅tion

  [ree-ak-shuhn]
Use reaction in a Sentence
–noun
1. a reverse movement or tendency; an action in a reverse direction or manner.
2. movement in the direction of political conservatism or extreme rightism.
3. action in response to some influence, event, etc.: the nation's reaction to the President's speech.
4. Physiology. action in response to a stimulus, as of the system or of a nerve, muscle, etc.
5. Medicine/Medical.
a. the action caused by the resistance to another action.
b. a return to the opposite physical condition, as after shock, exhaustion, or chill.
6. Bacteriology, Immunology. the specific cellular response to foreign matter, as in testing for allergies.
7. Chemistry. the reciprocal action of chemical agents upon each other; chemical change.
8. Also called nuclear reaction. Physics. a process in which a nucleus that is bombarded by a photon, particle, or other nucleus, emits a nucleon, alpha particle, or the like, without a significant change in its atomic weight.
9. Mechanics. the instantaneous response of a system to an applied force, manifested as the exertion of a force equal in magnitude but opposite in direction to the applied force.
10. Commerce. a decline in the market after an advance in prices.
Origin:
1635–45; re- + action, modeled on react

Related forms:
re⋅ac⋅tion⋅al, adjective
re⋅ac⋅tion⋅al⋅ly, adverb
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2009.
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re·ac·tion   (rē-āk'shən)   
n.  
    1. A response to a stimulus.
    2. The state resulting from such a response.
    3. A tendency to revert to a former state.
    4. Opposition to progress or liberalism; extreme conservatism.
  2. A reverse or opposing action.
    1. A tendency to revert to a former state.
    2. Opposition to progress or liberalism; extreme conservatism.
  4. Chemistry A change or transformation in which a substance decomposes, combines with other substances, or interchanges constituents with other substances.
  5. Physics A nuclear reaction.
  6. Physics An equal and opposite force exerted by a body against a force acting upon it.
  7. The response of cells or tissues to an antigen, as in a test for immunization.
The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Reaction

Re*ac"tion\, n. (Psycophysics) A regular or characteristic response to a stimulation of the nerves.

Reaction

Re*ac"tion\, n. [Cf. F. r['e]action.]

1. Any action in resisting other action or force; counter tendency; movement in a contrary direction; reverse action.

2. (Chem.) The mutual or reciprocal action of chemical agents upon each other, or the action upon such chemical agents of some form of energy, as heat, light, or electricity, resulting in a chemical change in one or more of these agents, with the production of new compounds or the manifestation of distinctive characters. See Blowpipe reaction, Flame reaction, under Blowpipe, and Flame.

3. (Med.) An action included by vital resistance to some other action; depression or exhaustion of vital force consequent on overexertion or overstimulation; heightened activity and overaction succeeding depression or shock.

4. (Mech.) The force which a body subjected to the action of a force from another body exerts upon the latter body in the opposite direction.

Reaction is always equal and opposite to action, that is to say, the actions of two bodies upon each other are always equal and in opposite directions. --Sir I. Newton (3d Law of Motion).

5. (Politics) Backward tendency or movement after revolution, reform, or great progress in any direction.

The new king had, at the very moment at which his fame and fortune reached the highest point, predicted the coming reaction. --Macaulay.

Reaction time (Physiol.), in nerve physiology, the interval between the application of a stimulus to an end organ of sense and the reaction or resulting movement; -- called also physiological time.

Reaction wheel (Mech.), a water wheel driven by the reaction of water, usually one in which the water, entering it centrally, escapes at its periphery in a direction opposed to that of its motion by orifices at right angles, or inclined, to its radii.
Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.
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Language Translation for : reaction
Spanish: reacción,
German: die Reaktion,
Japanese: 反応
More Translations »

reaction 
1611, from re- "again, anew" + action (q.v.). Modeled on Fr. réaction, older It. reattione, from M.L. reactionem (nom. reactio), from L.L. react-, pp. stem of reagere "react," from re- "back" + agere "to do, act" (see act). Originally scientific; physiological sense is attested from 1805; psychological sense first recorded 1887; general sense of "action or feeling in response" (to a statement, event, etc.) is recorded from 1914. The verb react is attested from 1644.
Online Etymology Dictionary, © 2001 Douglas Harper
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Reaction

The typical downward movement in the price of a security after the price had previously risen.

Investopedia Commentary

The opposite of a recovery, a reaction is similar to a market correction but lacks the same intensity.

See also: Break, Bulge, Correction, Futures Contract, Security

Investopedia.com. Copyright © 1999-2005 - All rights reserved. Owned and Operated by Investopedia Inc.
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reaction

A decline in security prices following a period of rising security prices.

Wall Street Words: An A to Z Guide to Investment Terms by David L. Scott.
Copyright © 2003. Published by Houghton Mifflin.
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Main Entry: re·ac·tion
Pronunciation: rE-'ak-sh&n
Function: noun
1 : the act or process or an instance of reacting
2 : bodily response to or activity aroused by a stimulus: a : an action induced by vital resistance to another action; especially : the response of tissues to aforeign substance (as an antigen or infective agent) b : depression or exhaustion due to excessive exertion or stimulation c : abnormally heightened activitysucceeding depression or shock d : a mental or emotional disorder forming an individual's response to his or her life situation
3 : the force that a body subjectedto the action of a force from another body exerts in the opposite direction
4 a (1) : chemical transformation or change : the interaction of chemical entities (2) : the state resulting from such a reaction b : a process involving change in atomic nuclei
Merriam-Webster's Medical Dictionary, © 2002 Merriam-Webster, Inc.
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reaction re·ac·tion (rē-āk'shən)
n.

  1. A response of an organism or living tissue to a stimulus.
  2. The state resulting from such a response.
  3. A chemical change or transformation in which a substance decomposes, combines with other substances, or interchanges constituents with other substances.
  4. The response of cells or tissues to an antigen, as in a test for immunization.
  5. 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.
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reaction   (rē-āk'shən)  Pronunciation Key 
  1. 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.
  2. See nuclear reaction.
  3. 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.
  4. A response to a stimulus, such as a reflex.
  5. The response of cells or tissues to an antigen, as in a test for immunization.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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