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 Then, a chemical reaction ignites the fireball and burns surrounding debris, stripping the area bare of fuel ahead of an oncoming wildfire. Matt Wyatt, ExpressNews.com, "The end of a year of fire at Anahuac National Wildlife Refuge," 7 Jan. 2021 Today, almost all working nuclear power plants use light water reactors, meaning a central nuclear fuel reaction cooled by regular, flowing water. Caroline Delbert, Popular Mechanics, "These 5 Advanced Nuclear Reactors Will Shape the Future of Energy," 5 Jan. 2021 Each time, the plucky robot climbs back onto its feet—and not because the researchers coded this reaction to this particular variety of assault, but because the Jueying is now consulting with its AI experts in the art of locomotion. Matt Simon, Wired, "Watch a Robot Dog Learn How to Deftly Fend Off a Human," 5 Jan. 2021 Adams was seen throwing his helmet to the turf during the game against the 49ers, likely a reaction to his latest injury. oregonlive, "Seattle Seahawks unsure of Jamal Adams’ availability for Wild Card playoff game," 5 Jan. 2021 The new money drew a mixed reaction from nonprofit groups running the food lines. Washington Post, "At Ivanka Trump’s urging, White House announces new $1.5 billion in funding for Farmers to Families Food Box program," 4 Jan. 2021 Campanario declined to say whether audience reaction to Season 1 might force any changes before the next season streams. Los Angeles Times, "Here are the top Latino media moments of 2020 — and hints of what to expect in 2021," 31 Dec. 2020 Rodgers did that at times in 2019, too often probably, and the network cameras would capture LaFleur’s reaction at times standing on the sideline during games. Brad Biggs, chicagotribune.com, "Column: Aaron Rodgers is playing at an MVP level in Year 2 of Matt LaFleur’s offense. Now the QB and the Green Bay Packers stand between the Chicago Bears and the playoffs.," 31 Dec. 2020 As much as 5% of people in the U.S. have had such a reaction to various substances. John Lauerman, Fortune, "Everything to know about allergic reactions to COVID vaccines," 31 Dec. 2020

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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Statistics for reaction

Last Updated

14 Jan 2021

Cite this Entry

“Reaction.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/reaction. Accessed 23 Jan. 2021.

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More Definitions for reaction

reaction

noun
How to pronounce reaction (audio)

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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