re·​act | \rē-ˈakt \
reacted; reacting; reacts

Definition of react 

intransitive verb

1 : to exert a reciprocal or counteracting force or influence often used with on or upon

2 : to change in response to a stimulus

3 : to act in opposition to a force or influence usually used with against

4 : to move or tend in a reverse direction

5 : to undergo chemical reaction

transitive verb

: to cause to react

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Synonyms for react


reply, respond

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Examples of react in a Sentence

When I told her what happened, she reacted with anger. I didn't expect him to react that way. The firefighters reacted quickly when they heard the alarm. He reacted badly to the drug.
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Recent Examples on the Web

Mediation is also a place for perpetrators, or harm-doers, to react. Kim Tran, Teen Vogue, "Transformative Justice, Explained," 15 Nov. 2018 Put in less-evocative language: Vector is designed to be curious and to react. Dieter Bohn, The Verge, "The new Anki Vector robot is smart enough to just hang out," 8 Aug. 2018 Then, as the temperature increases, the sugars break down and react together to form yet more tasty new molecules, darkening the mixture and adding that distinctive caramel tang. Helen Czerski, WSJ, "The Sugary Coats of Holiday Apples," 15 Nov. 2018 But why do users have to suffer before Microsoft reacts? Mark Hachman, PCWorld, "Microsoft restarts Windows 10 October 2018 Update, blaming data loss on misdirected folders," 9 Oct. 2018 One friend from naval academy days recalls John reacted to seeing an upperclassman verbally abuse a steward. Lauren Hubbard, Town & Country, "Read the Full Transcript of George W. Bush's Eulogy for John McCain," 1 Sep. 2018 Perisic beat Walker to the ball to equalise, and Stones reacted later than Mandzukic in the lead up to the winner., "England: Who Is to Blame?," 12 July 2018 Neymar reacted in hysterics, prompting a furious response from both benches., "Neymar Fires Back at Critics Trying to 'Undermine’ Him Following Play Acting Accusations," 3 July 2018 Upon hearing that news, his teammates Donovan Mitchell and Rudy Gobert reacted by quickly posting similar requests on Twitter — that being that Favors finally grabs a dinner check. Tim Reynolds, The Seattle Times, "Boogie Bomb: Warriors set to add DeMarcus Cousins to lineup," 3 July 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'react.' 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 react

1644, in the meaning defined at intransitive sense 1

History and Etymology for react

New Latin reactus, past participle of reagere, from Latin re- + agere to act — more at agent

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Statistics for react

Last Updated

9 Dec 2018

Look-up Popularity

Time Traveler for react

The first known use of react was in 1644

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More Definitions for react



English Language Learners Definition of react

: to behave or change in a particular way when something happens, is said, etc.

of a chemical substance : to change after coming into contact with another substance

medical : to be affected by a drug, food, etc., in usually a bad way


re·​act | \rē-ˈakt \
reacted; reacting

Kids Definition of react

1 : to act or behave in response to something Firefighters reacted quickly to the situation.

2 : to oppose a force or influence

Hint: In this sense, react is usually used with against.
  • Workers reacted against unfair treatment.

3 : to go through a chemical reaction Acids react with bases to form salt.

re·​act | \rē-ˈakt \

Medical Definition of react 

1 : to respond to a stimulus

2 : to undergo chemical reaction

transitive verb

: to cause to react

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More from Merriam-Webster on react

Rhyming Dictionary: Words that rhyme with react

Thesaurus: All synonyms and antonyms for react

Spanish Central: Translation of react

Nglish: Translation of react for Spanish Speakers

Britannica English: Translation of react for Arabic Speakers

Comments on react

What made you want to look up react? Please tell us where you read or heard it (including the quote, if possible).


a nest or breeding place

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