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English definition of “react”

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react

verb [I] uk   /riˈækt/ us  
B2 to act in a particular way as a direct result of something else: She slapped him and called him names, but he didn't react. The judge reacted angrily to the suggestion that it hadn't been a fair trial. Many people react (badly) to (= are made ill by) penicillin. chemistry to change in a physical or chemical way when put with another substance: Potassium reacts with water.
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(Definition of react from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
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