Definitions for: Reaction

[n] doing something in opposition to another way of doing it that you don't like; "his style of painting was a reaction against cubism"
[n] a bodily process occurring due to the effect of some foregoing stimulus or agent; "a bad reaction to the medicine"; "his responses have slowed with age"
[n] an idea evoked by some experience; "his reaction to the news was to start planning what to do"
[n] extreme conservatism in political or social matters; "the forces of reaction carried the election"
[n] a response that reveals a person's feelings or attitude; "he was pleased by the audience's reaction to his performance"; "John feared his mother's reaction when she saw the broken lamp"
[n] (mechanics) the equal and opposite force that is produced when any force is applied to a body; "every action has an equal and opposite reaction"
[n] (chemistry) a process in which one or more substances are changed into others; "there was a chemical reaction of the lime with the ground water"

Webster (1913) Definition: Re*ac"tion, n. (Psycophysics)
A regular or characteristic response to a stimulation of the

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

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

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.

Synonyms: chemical reaction, response

See Also: activity, addition reaction, aldol reaction, answer, automatism, backlash, bodily function, bodily process, body process, chain reaction, chemical action, chemical change, chemical equilibrium, chemical process, conservatism, conservativism, decomposition, decomposition reaction, displacement, displacement reaction, double decomposition, double decomposition reaction, double take, electrical skin response, electrodermal response, elimination reaction, endothermic reaction, equilibrium, exothermic reaction, Fere phenomenon, force, galvanic skin response, GSR, hydrolysis, idea, immune reaction, immune response, immunologic response, inborn reflex, innate reflex, instinctive reflex, kinesis, learned reaction, learned response, metathesis, neutralisation, neutralisation reaction, neutralization, neutralization reaction, opposition, overreaction, oxidation, oxidation-reduction, oxidisation, oxidization, oxidoreduction, passage, passing, photochemical reaction, physiological reaction, psychogalvanic response, rebound, redox, reducing, reduction, reflex, resistance, response, saponification, Tarchanoff phenomenon, taxis, thought, transfusion reaction, tropism, unconditioned reflex

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