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 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
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

Some adverse reactions to look out for can be diarrhea and bellyaches. If your canine (and their stomach) loves the new snack, then great. Jackie Frere, Woman's Day, "Can Dogs Eat Apples? A Veterinarian Weighs In," 2 Apr. 2019 And based on this week's online reactions, that is looking more and more like a very good thing. Kayla Keegan, Good Housekeeping, "'American Idol' Fans Are Going After Luke Bryan After Judges' "HORRIBLE Decision" in Top 20 Episode," 1 Apr. 2019 There’s a short reveal trailer below, including glimpses of chain-reaction combat mishaps and the squad selection screen. Hayden Dingman, PCWorld, "This week in games: Free copies of Morrowind, Divinity: Original Sin 2 gets a tactics spinoff," 25 Mar. 2019 The finished product has always been my favorite part, with new colors, layouts, furniture, and the homeowner's reaction, of course. Elizabeth Gulino, House Beautiful, "Forget Doghouses—This Dog Has His Own Village," 28 Feb. 2019 If the system starts pushing the plane’s nose down, pilots can reverse the movement via a switch at their thumb, a typical reaction in that situation. Eric Limer, Popular Mechanics, "Lion Air Pilots Had Less Than a Minute to Avert Fatal Crash," 27 Mar. 2019 Fans have been waiting for this moment for a while now, and the reactions online prove it. Christopher Rosa, Allure, "Lady Gaga Slams Pregnancy Rumors, and Then Announces New Music," 13 Mar. 2019 Her husband Dave, having planned this entire thing, caught her reaction on video. Kelly O'sullivan, Country Living, "This Video of Kelly Clarkson Surprising a Fan Is So Intense, Words Don't Do It Justice," 12 Mar. 2019 Crew Dragon's arrival was marked by celebrations from ISS crew members, who posted their jubilant reactions to Twitter. Sam Blum, Popular Mechanics, "SpaceX's First Manned Mission to The ISS Could Come as Quickly as July," 4 Mar. 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

18 Apr 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 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
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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