re·​act | \ rē-ˈakt How to pronounce react (audio) \
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


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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 One exception is the Govee light strip, which has a mic that activates in music mode, so its LEDs can react to sound in the room. Simon Hill, Wired, "How to Use Smart Lighting to Transform Your Kid’s Bedroom," 15 Apr. 2021 In seeking answers to these and other questions, computer scientists are now trying to enable AIs that can react properly to the unexpected, including black-swan events like COVID-19. Mayank Kejriwal, The Conversation, "Embrace the unexpected: To teach AI how to handle new situations, change the rules of the game," 7 Apr. 2021 The latest recommendations from Singapore envision a workplace that’s geared to switch quickly to a ‘pandemic-on’ mode so that companies can react to future pandemics. Faris Mokhtar, Fortune, "Singapore publishes a playbook for bringing bankers back into the office," 23 Mar. 2021 When combined with nitrogen oxide, the two can react and form the pollutant ozone, or smog. Halle Parker | Staff Writer,, "Environmental groups oppose Shintech's Louisiana expansion over air pollution concerns," 2 Feb. 2021 Users can only react or respond to them with direct messages, much like on Instagram and Snapchat. Kaya Yurieff, CNN, "Twitter is evolving beyond tweets," 17 Nov. 2020 Readers can react to investigative reporting on, say, Trump’s taxes with a shrug. Chris Jones,, "Will we ever learn? Hubris by both a president and the news media on a tense Tuesday election night," 4 Nov. 2020 In their new laboratory experiment, Stafstrom and colleagues inserted tiny electrodes into spiders’ brains and also into disembodied legs, which can react to sounds up to an hour after being severed. Liz Langley, National Geographic, "Ogre-faced spiders have great hearing—without ears," 29 Oct. 2020 Individuals typically react more rapidly than governments do. Tomas J. Philipson, National Review, "The Vaccine Rollout and COVID Déjà Vu," 2 Apr. 2021

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

17 Apr 2021

Cite this Entry

“React.” Dictionary, Merriam-Webster, Accessed 20 Apr. 2021.

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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 How to pronounce react (audio) \
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 How to pronounce react (audio) \

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

Thesaurus: All synonyms and antonyms for react

Nglish: Translation of react for Spanish Speakers

Britannica English: Translation of react for Arabic Speakers

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