effective - definition and synonyms


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  1. 1
    someone or something that is effective works well and produces the result that was intended

    You need more effective communication within the organization.

    Humour is often far more effective than shouting.

    The troops should be deployed where they will be most effective.

    effective against:

    The new vaccine is highly effective against all strains of the disease.

    effective way/method/means:

    This is a very effective way of controlling pests and weeds.

  2. 2
    formal when a law or agreement becomes effective, it officially begins to be used
    effective from:

    Government ministers reached a 30-month agreement, effective from 1 July.

  3. 3
    [only before noun] used for saying what the situation really is, although its appearance or official description might be different

    The US military is in effective control of the entire region.

    1. a.
      used for saying what is really having a particular effect, although other things may be involved in a situation

      the effective agents in the spread of the disease

derived word



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noun [uncountable]