Dictionary.net

an idea evoked by some experience; "his reaction to the news was to start planning what to do"

extreme conservatism in political or social matters; "the forces of reaction carried the election"

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"

(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"

an idea evoked by some experience; "his reaction to the news was to start planning what to do"

extreme conservatism in political or social matters; "the forces of reaction carried the election"

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"

(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"

A regular or characteristic response to a stimulation of the nerves.

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.

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

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.

An action induced 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.

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

Backward tendency or movement after revolution, reform, or great progress in any direction.

A regular or characteristic response to a stimulation of the nerves.

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.

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

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.

An action induced 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.

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

Backward tendency or movement after revolution, reform, or great progress in any direction.

Return action or influence; response to influence or effort exerted; a return to a former or opposite state of things; contrary action following the effects of other action; the equal force that a body exerts on an opposing force; chemical change; a chemical process or its result.

The response of a muscle or other living tissue to a stimulus. 2. The color change affected in litmus and certain other organic pigments by contact with various substances (acids or alkalies); also the property which such substances possess of producing this change. 3. In chemistry the intermolecular action of two or more substances upon each other, whereby these substances are caused to disappear, new ones being formed in their place.

That which is produced by a reagent.

Action following and contrary to previous action; mutual action.

Reactive, reactionary.

Reverse or return action.

The mutual action of chemical agents, or its result.

Counteraction; reciprocal action; action in the contrary, specially backward, direction.

The resistance made by a body to the action or impulse of another body; an action or force arising in opposition to another which has preceded.

An action of resistance to a power applied. A species of vital movement or excitement, tending to prevent or destroy the effects of any noxious power applied to the animal economy, and which, by some, has been attributed to the vis medicatrix naturae. It is certainly dependent on the organic instinctive actions of the frame. It is the state of activity which succeeds the action on the nervous system of certain morbific influences.

Opposite action or counter-action.

Phenomena caused by chemical action of substances on each other.

In chemistry, a physical phenomenon occurring on the application of a chemical test, and hence indicative of the possession of a special chemical property; also, a physical phenomenon indicative of a change in the chemical state of a body; hence the change of state itself, whether this is brought about by the molecular interaction of two or more substances or the application of a physical force.

In psycho-analysis the psychical response to an emotional situation.

The process of recovery from "shock".

The development of fever as the result of an injury, a surgical operation, or the like.

n. Any action in resisting other action or power; counter tendency or movement ;-the mutual or reciprocal action of chemical agents upon each other ;--depression of vital force consequent on over-exertion ;-backward tendency from revolution, reform, or progress.