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 Here antibodies, formed in response to the virus, react to proteins found on nerves, causing damage. Dr. Minali Nigam And Dr. Sanjay Gupta, CNN, "We're only just beginning to learn how Covid-19 affects the brain," 29 July 2020 Evers did not immediately react to the ruling, but Rick Esenberg, the president of the institute that brought the lawsuit, hailed the decision. Milwaukee Journal Sentinel, "In a blow to Gov. Tony Evers, state Supreme Court overturns three budget vetoes," 10 July 2020 The lights can even react to sound, lighting up and changing colors, for example, as fireworks explode outside. Jason Cipriani, CNN Underscored, "All the smart lights and speakers to light up your home for the Fourth of July," 1 July 2020 Candidates react Knight, one of Gunnigle's opponents, sent a letter to the Maricopa County Democratic Party about his thoughts on the incident. Lauren Castle, The Arizona Republic, "Maricopa County attorney candidate accused of misconduct in decade-old case," 1 July 2020 Some are also running out of the chemical reagent that must react with a testing specimen. Robinson Meyer, The Atlantic, "U.S. Coronavirus Testing Could Fail Again," 30 June 2020 Giant hogweed’s particularly nasty blistering rash emerges when people are exposed to chemical compounds within the plant that then react to sunlight. cleveland, "Poison ivy and other pesky plants can turn summer fun into a season of suffering," 30 June 2020 Redfield said the new, much-higher estimate, is based on growing data from antibody testing, which picks up the presence of immune cells that react to SARS-CoV-2, the virus that causes COVID-19. Alice Park, Time, "CDC Head Estimates U.S. Coronavirus Cases Might be 10 Times Higher Than Data Show," 25 June 2020 For example, some of the young gorillas, known for their mischievous antics, like to play, wrap banana leaves around their heads and roll down the hill, right at the viewing spot frequented by guests, who’d react with laughter and pointing. Lisa A. Beach, Condé Nast Traveler, "How Walt Disney World Is Caring for Its 10,000 Animals While Parks Are Closed," 15 June 2020

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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Time Traveler for react

Time Traveler

The first known use of react was in 1644

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Statistics for react

Last Updated

2 Aug 2020

Cite this Entry

“React.” Dictionary, Merriam-Webster, Accessed 6 Aug. 2020.

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More Definitions for react


How to pronounce react (audio)

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

Rhyming Dictionary: Words that rhyme with react

Spanish Central: Translation of react

Nglish: Translation of react for Spanish Speakers

Britannica English: Translation of react for Arabic Speakers

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