Hypertext Webster Gateway: "reaction"

From Webster's Revised Unabridged Dictionary (1913) (web1913)

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

From Webster's Revised Unabridged Dictionary (1913) (web1913)

Widal's \Wi*dal's"\, or Widal test \Wi*dal", test\ or reaction
\reaction\ . [After Fernand Widal (b. 1862), French physician.]
(Med.)
A test for typhoid fever based on the fact that blood serum
of one affected, in a bouillon culture of typhoid bacilli,
causes the bacilli to agglutinate and lose their motility.

From Webster's Revised Unabridged Dictionary (1913) (web1913)

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.

From WordNet (r) 1.7 (wn)

reaction
n 1: 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"
2: 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" [syn: {response}]
3: (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" [syn: {chemical reaction}]
4: an idea evoked by some experience; "his reaction to the news
was to start planning what to do"
5: doing something in opposition to another way of doing it
that you don't like; "his style of painting was a reaction
against cubism"
6: extreme conservatism in political or social matters; "the
forces of reaction carried the election"
7: (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"


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