Dictionary

reaction

noun re·ac·tion \rē-ˈak-shən\

: the way someone acts or feels in response to something that happens, is said, etc.

: an action or attitude that shows disagreement with or disapproval of someone or something

reactions : the ability to act and move quickly in order to avoid sudden danger

Full Definition of REACTION

1
a :  the act or process or an instance of reacting
b :  resistance or opposition to a force, influence, or movement; especially :  tendency toward a former and usually outmoded political or social order or policy
2
:  a response to some treatment, situation, or stimulus <her stunned reaction to the news>; also :  such a response expressed verbally <critical reaction to the play>
3
:  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 stimulation
c :  heightened activity and overaction succeeding depression or shock
d :  a mental or emotional disorder forming an individual's response to his or her life situation
4
:  the force that a body subjected to the action of a force from another body exerts in the opposite direction
5
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
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Examples of REACTION

  1. Their reaction to the news was positive.
  2. When I told him what happened, his immediate reaction was one of shock.
  3. The announcement produced an angry reaction from most of the people at the meeting.
  4. My first reaction when I met him was not to trust him.
  5. There hasn't yet been much reaction to the announcement.
  6. There has been strong reaction against the government's policies.
  7. A good driver has quick reactions.
  8. The speed of his reactions saved his life.

First Known Use of REACTION

circa 1611
REACTIONS Defined for Kids

reaction

noun re·ac·tion \rē-ˈak-shən\

Definition of REACTION for Kids

1
:  behavior or attitude in response to something <What was your reaction to the news?>
2
:  a response of the body to a stimulus <He had an allergic reaction to peanuts.>
3
:  a chemical change that is brought about by the action of one substance on another and results in a new substance being formed
Medical Dictionary

reaction

noun re·ac·tion \rē-ˈak-shən\

Medical Definition of REACTION

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 a foreign substance (as an antigen or infective agent) b :  depression or exhaustion due to excessive exertion or stimulation c :  abnormally heightened activity succeeding 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 subjected to 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
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