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

answer, reply, response, take

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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 Premier League new-boys stunned the champions when Kenny McLean powered a near-post header into the top corner, though questions will be asked of Ederson's reactions and positioning. SI.com, "Norwich 3-2 Manchester City: Report, Ratings & Reaction as Canaries Conquer Champions," 14 Sep. 2019 But the more diverse lineup drew mixed reactions on social media. Marie C. Baca, Washington Post, "More women and people of color took the stage at Apple’s big event. Was it enough?," 11 Sep. 2019 The 10-member boy band saw a majority of their activity coming from Twitter for the tracking week of Aug. 23-29, scoring 161,000 Twitter reactions and 75,000 Twitter mentions to bow on the ranking. Jeff Benjamin, Billboard, "Up10tion Debut on Social 50 Following Release of New Album 'The Moment of Illusion'," 9 Sep. 2019 Three patients in Florida suffered irreversible eye damage after fat extracts were injected into their eyes to treat macular degeneration, and reports of other serious side effects and reactions are not uncommon. Lloyd Minor, Fortune, "Why Google’s Crackdown on Fake Medicine Is So Important," 9 Sep. 2019 Laureano, who went 2 for 3 on Saturday, missed 32 games, including all of August, after suffering a right lower leg stress reaction on July 29. Jeff Faraudo, The Mercury News, "A’s reliever Yusmeiro Petit will honor his father in appropriate way," 8 Sep. 2019 Adrian’s fast reaction and fast exposure captured the shocking drama. Johnny Simon, Quartz, "A year’s worth of surprising and poignant nature photos," 8 Sep. 2019 The disease is caused by genetic and environmental factors — sun exposure, infections and reactions to medications can all bring it out, though the cause is often unknown. Julie Mazziotta, PEOPLE.com, "Kim Kardashian Believes She Has Lupus in New KUWTK Trailer: ‘I Feel This in My Bones’," 5 Sep. 2019 Loewe’s post had received over 750K reactions on Facebook as of Thursday afternoon. Alexandra Deabler, Fox News, "Teacher’s back to school 'Baggage Activity' praised for powerful message: 'It brings me to tears'," 29 Aug. 2019

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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Statistics for reaction

Last Updated

19 Sep 2019

Look-up Popularity

Time Traveler for reaction

The first known use of reaction was in 1585

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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

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Comments on reaction

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