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reaction

n.
US //ɹiˈækʃən// UK //ɹɪˈækʃən// re·ac·tion
  1. 1 response to an event (n.)
    B1 Intermediate

    something you say, feel, or do because of something else that happened.

    a physiological or psychological response to a stimulus or event.

    Example

    His first reaction to the news was a look of pure surprise.

    Example

    The public reaction to the proposed tax increase was overwhelmingly negative, forcing the local council to reconsider its budget priorities.

  2. 2 chemical change (n.)
    B2 Upper Intermediate Technical Science

    a process where two or more substances change into something new.

    a process involving the rearrangement of the molecular or ionic structure of a substance.

    Example

    The chemical reaction caused the liquid to turn bright green.

    Example

    The catalyst was added to accelerate the reaction, ensuring that the compound reached stability before the temperature dropped.

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  1. 3 online emoji (n.)
    B1 Intermediate Informal Computing

    an icon or emoji you use to show how you feel about a post on social media.

    a digital feedback mechanism, typically an emoji, used to express a specific sentiment toward online content.

    Example

    She got over fifty heart reactions on her new photo.

    Example

    The platform introduced several new reactions, allowing users to express nuanced emotions beyond a simple 'like' button.

  2. 4 political resistance (n.)
    C1 Advanced Academic Formal Politics

    a movement that opposes social or political change.

    opposition to political or social progress or reform; reactionary policy.

    Example

    The new law met with strong reaction from traditional groups.

    Example

    The revolution was followed by a period of intense political reaction, as the old elite sought to dismantle the newly established democratic institutions.

Origin

Inherited from Middle English reaccion, from Old French reaction, from Latin reāctiō, from the verb reagō, from re- (“again”) + agō (“to act”); more at re-, action; equivalent to react + -ion.

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