reaction - definition and synonyms


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  1. 1
    [countable] the way that you feel or behave as a result of something that happens

    My mother’s initial reaction was quite unexpected.

    1. a.
      [usually singular] a sudden feeling of being tired, upset etc, for example after an unpleasant or exciting experience

      The reaction of any individual trauma victim is difficult to predict.

      reaction to:

      Shock is a natural reaction to such bad news.

    See also knee-jerk
  2. 2
    [countable] a bad effect on your body caused by food, medicine, or another substance
    reaction to:

    Some people’s skin has an allergic reaction to certain types of fabric.

    have/suffer a reaction:

    He suffered a violent reaction to the medicine.

  3. 4
    [countable] chemistry a process in which a chemical change happens

    Temperature can affect the rate of a chemical reaction.

    reaction between:

    We are studying reactions between a number of metals and acids.

    1. a.
      [countable/uncountable] physics a physical force that is caused by an opposite physical force, usually producing a form of energy

      a nuclear reaction

      Newton teaches that action and reaction are equal and opposite.

    See also chain reaction
  4. 5
    [singular] an attitude of wanting to do things in a different way from the way that they were done in the past
    reaction against:

    The reaction against traditional styles continued for another 50 years.