reaction

noun
re·​ac·​tion | \ rē-ˈak-shən How to pronounce reaction (audio) \

Definition of reaction

1a : 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 infectious 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
5a(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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Synonyms for reaction

Synonyms

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Examples of reaction in a Sentence

Their reaction to the news was positive. When I told him what happened, his immediate reaction was one of shock. The announcement produced an angry reaction from most of the people at the meeting. My first reaction when I met him was not to trust him. There hasn't yet been much reaction to the announcement. There has been strong reaction against the government's policies. A good driver has quick reactions. The speed of his reactions saved his life.
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Recent Examples on the Web The reason is misinformation for sure, and more fundamentally a lacuna in thinking prompted by an emotional reaction. Ryan Craig, Forbes, 15 Oct. 2021 The findings could also support the idea that long Covid may be caused by an autoimmune reaction, Dr. Iwasaki says. Sumathi Reddy, WSJ, 11 Oct. 2021 And then season 1 happened and I was just bowled over by the reaction to the show and to people embracing Nate's underdog story line. Derek Lawrence, EW.com, 8 Oct. 2021 Informed by crowd reaction to live performances, Humilde has signed mostly local, underground regional Mexican acts since 2011, fueling their success with a nontraditional digital marketing approach that initially didn’t rely on radio or TV. Billboard Staff, Billboard, 7 Oct. 2021 Her son, Jeet Kamal, was left disabled by a severe reaction to a vaccine as a baby and required round-the-clock care. BostonGlobe.com, 5 Oct. 2021 Ashford is not surprised by Jones’ negative reaction to the series. Meredith Blake Staff Writer, Los Angeles Times, 5 Oct. 2021 Judging by his reaction to Peter on that TV, Venom clearly knows something about Spider-Man. Ryan Britt, Vulture, 1 Oct. 2021 His pleas were interrupted by an enthusiastic reaction to the singers on stage. Phil Gallo, Variety, 30 Sep. 2021

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.

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First Known Use of reaction

1585, in the meaning defined at sense 1a

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Time Traveler for reaction

Time Traveler

The first known use of reaction was in 1585

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Dictionary Entries Near reaction

reactant

reaction

reactional

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Statistics for reaction

Last Updated

17 Oct 2021

Cite this Entry

“Reaction.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/reaction. Accessed 18 Oct. 2021.

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More Definitions for reaction

reaction

noun

English Language Learners Definition of reaction

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

reaction

noun
re·​ac·​tion | \ rē-ˈak-shən How to pronounce reaction (audio) \

Kids Definition of reaction

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

reaction

noun
re·​ac·​tion | \ rē-ˈak-shən How to pronounce reaction (audio) \

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 infectious 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
4a(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

More from Merriam-Webster on reaction

Nglish: Translation of reaction for Spanish Speakers

Britannica English: Translation of reaction for Arabic Speakers

Britannica.com: Encyclopedia article about reaction

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