Definition of react in English:


Syllabification: re·act
Pronunciation: /rēˈakt


[no object]
  • 1Respond or behave in a particular way in response to something: he reacted angrily to the news of his dismissal the market reacted by falling a further 3.1%
    More example sentences
    • Rail passengers have reacted angrily to news that fares are set to rise.
    • All my three daughters react differently to stress.
    • One reason is that financial markets react quickly to policy changes.
    behave, act, take it, conduct oneself; respond, reply, answerrebel against, oppose, rise up against
  • 1.1 (react against) Respond with hostility, opposition, or a contrary course of action to: they reacted against the elite art music of their time
    More example sentences
    • Workers reacted against the outrageous contract demands of the company, voting by an overwhelming 48 to 3 for strike action.
    • How do we react against such violence and war in our time?
    • Third, many people in the younger generation, under age 30 or so, are reacting against the culture of divorce.
  • 1.2(Of a person) suffer from adverse physiological effects after ingesting, breathing, or touching a substance: many babies react to soy-based formulas
    More example sentences
    • Therefore you can suddenly react to a substance you may have come in contact with many times before.
    • Why do some members of a family react to environmental substances and develop asthma, while others do not?
    • Our findings indicate that children at risk for atopy react sensitively to chemical substances that originate from passive smoking.
  • 1.3 Chemistry & Physics Interact and undergo a chemical or physical change: the sulfur in the coal reacts with the limestone during combustion
    More example sentences
    • When base is added, it reacts with hydronium ion to decrease its concentration, thereby stressing the system.
    • In these reactions the ozone reacts with nitric oxide to produce nitrogen dioxide.
    • Direct sensing mechanisms might involve proteins or ligands that bind or react with oxygen.
  • 1.4 [with object] Chemistry Cause (a substance) to undergo a change by interacting with another substance.
    More example sentences
    • These materials are reacted with sulfuric acid, then neutralized, and converted to a salt.
    • Organic sulfates are esters and are formed by reacting an alcohol with cold sulfuric acid or by the reaction of sulfuric acid with a double bond in an alkene.
    • Many alkyl halides, alcohols, or alkenes can be reacted with benzene in the presence of certain catalysts to give an alkyl benzene.
  • 1.5 Stock Market (Of stock prices) fall or rise in reaction to events, developments, etc..
    More example sentences
    • Edging down a bit from record highs, but maybe not for long, oil prices react to events in Iraq.
    • The stock price is reacting, up some 50 percent to $15 a share since Payne took charge.
    • Just how will bond markets and stock markets react to the anticipated rise in US interest rates?


mid 17th century: from re- (expressing intensive force or reversal) + act, originally suggested by medieval Latin react- 'done again', from the verb reagere.

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