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English definition of “reaction”

reaction

noun     /riˈækʃən/
CAUSED BY SOMETHING [C, U] B2 something you say, feel, or do because of something that has happened: What was his reaction to the news?Reacting and responding
reactions mainly UK the ability to move quickly when something suddenly happens: Drivers need to have quick reactions.Reacting and responding
CHANGE [no plural] a change in the way people behave or think because they do not agree with the way people behaved or thought in the past: In art, there was a reaction against Realism.Reacting and responding
BAD EFFECT [C] B2 an unpleasant feeling or illness caused by something you have eaten or used on your body: A number of people have had a bad reaction to this drug.Reacting and responding
SUBSTANCES [C] a change that happens when two substances are put together: a chemical reaction → See also chain reactionPhysical and chemical processes
(Definition of reaction noun from the Cambridge Learner's Dictionary © Cambridge University Press)

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