reaction

noun re·ac·tion \ rē-ˈak-shən \
Updated on: 15 Nov 2017

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 (such 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

Examples of reaction in a Sentence

  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.

Recent Examples of reaction from the Web

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'reaction.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of reaction

1585

reaction Synonyms



REACTION Defined for English Language Learners

reaction

noun

Definition of reaction for English Language Learners

  • : 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


REACTION Defined for Kids

reaction

noun re·ac·tion \ rē-ˈak-shən \

Definition of reaction for Students

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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