reaction

noun

re·ac·tion | \ rē-ˈak-shən

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

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.

Recent Examples on the Web

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 While baby noticing a different flavor isn’t necessarily bad, keep a keen eye on her reactions to common allergens such as dairy or wheat. — Karla Walsh, Woman's Day, "The Best Breastfeeding Diet," 25 Feb. 2019 Watch his reaction in the clip below, captured by royal reporter Rebecca English. — Chloe Foussianes, Town & Country, "For Prince Harry's Visit, Soldiers Decorated an Igloo With Photos of His and Meghan Markle's Wedding," 14 Feb. 2019 Or new chemical reactions that require a lot less energy and have a lot less waste. — David Roberts, Vox, "Climate change policy can be overwhelming. Here’s a guide to the policies that work.," 30 Nov. 2018 Growing as both a shrub and a vine, the innocuous-looking flora produces a noxious sap responsible for the reaction, called allergic contact dermatitis. — Caroline Picard, Good Housekeeping, "How to Get Rid of a Poison Ivy Rash and Stop Itching Like Crazy," 13 July 2018 Mexico’s currency weakened and Pemex bond prices fell in reaction to the announcement. — Robbie Whelan, WSJ, "Mexico Unveils Plan to Support State Oil Company Pemex," 15 Feb. 2019 At her childhood home, standards and rules were forged in reaction to the city’s ever-transforming chaos outside. — Marley Marius, Vogue, "Family Furniture: Meet the Artist Turning Her Parents and Grandparents Into Chairs," 18 Jan. 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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Dictionary Entries near reaction

Statistics for reaction

Last Updated

21 Mar 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

See the full definition for reaction in the English Language Learners Dictionary

reaction

noun

re·ac·tion | \ rē-ˈak-shən

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

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