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Medical Dictionary

reaction

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noun re·ac·tion \rē-ˈak-shən\

Medical Definition of reaction

  1. 1:  the act or process or an instance of reacting

  2. 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 a foreign substance (as an antigen or infective agent)b:  depression or exhaustion due to excessive exertion or stimulationc:  abnormally heightened activity succeeding depression or shockd:  a mental or emotional disorder forming an individual's response to his or her life situation

  3. 3:  the force that a body subjected to the action of a force from another body exerts in the opposite direction

  4. 4a (1):  chemical transformation or change :  the interaction of chemical entities (2):  the state resulting from such a reactionb:  a process involving change in atomic nuclei





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