Definition of reaction noun from the Oxford Advanced Learner's Dictionary



    BrE BrE//riˈækʃn//
    ; NAmE NAmE//riˈækʃn//
    Molecules and matter, Medication
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  1. 1  [countable, uncountable] reaction (to somebody/something) what you do, say or think as a result of something that has happened What was his reaction to the news? My immediate reaction was one of shock. A spokesman said the changes were not in reaction to the company's recent losses. There has been a mixed reaction to her appointment as director. The decision provoked an angry reaction from local residents. I tried shaking him but there was no reaction.
  2. change in attitudes
  3. 2  [countable, usually singular, uncountable] reaction (against something) a change in people’s attitudes or behaviour caused by disapproval of the attitudes, etc. of the past The return to traditional family values is a reaction against the permissiveness of recent decades.
  4. to drugs
  5. 3  [countable, uncountable] a response by the body, usually a bad one, to a drug, chemical substance, etc. to have an allergic reaction to a drug See related entries: Medication
  6. to danger
  7. 4  reactions [plural] the ability to move quickly in response to something, especially if in danger a skilled driver with quick reactions
  8. science
  9. 5   [countable, uncountable] (chemistry) a chemical change produced by two or more substances acting on each other a chemical/nuclear reaction see also chain reaction See related entries: Molecules and matter
  10. 6 [uncountable, countable] (physics) a force shown by something in response to another force, which is of equal strength and acts in the opposite direction Action and reaction are equal and opposite.
  11. against progress
  12. 7 [uncountable] opposition to social or political progress or change The forces of reaction made change difficult.
  13. Word Originmid 17th cent.: from react + -ion, originally suggested by medieval Latin reactio(n-), from react- ‘done again’, from the verb reagere.Extra examples Alcohol has the effect of slowing down your reactions. He eyed her cautiously, trying to gauge her reaction. Her outburst was a delayed reaction to an unpleasant letter she’d received that morning. Her rebellious attitude is just a reaction against her strict upbringing. His reaction is completely understandable. I am studying the reactions between certain gases. I believe she is experiencing a post-traumatic stress reaction. Judging by her reaction, she liked the present. Keenan showed lightning reactions. She had a very bad allergic reaction to the peanuts. She has very quick reactions. She was surprised at the reaction brought by the mention of his name. The change of plan set off a chain reaction of confusion. The critical reaction to his first novel has been positive. The incident calls for a measured response, avoiding knee-jerk reactions. The play met with a mixed reaction from the critics. The speech got a mixed reaction. There’s been a drop in ticket sales in reaction to the review. Your reaction time increases when you are tired. a delayed reaction to the drugs the energy given out during the reaction the fuel’s chemical reaction with the surrounding water the public reaction to the news A spokesman said the changes were not in reaction to the company’s recent losses.
See the Oxford Advanced American Dictionary entry: reaction