US /ɪˈfɛktɪv/
adj Freq #4069

Meanings

  1. 1
    adj

    Working well and producing the result you want.

    The pill is an effective method of birth control.

  2. 2
    adj

    Officially in operation; starting to apply.

    The new rules are effective immediately.

Thesaurus

Synonyms
1 adj · working well and producing... efficaciouseffectual
2 adj · officially in operation;... in effectin force
Word family
Derived forms bioeffectivecoeffectivecost-effectiveeffectivateeffectivelyeffectivenesseffectivizationeffectivizeeffieequieffectivegeoeffectiveineffective

Etymology

From French effectif, from Latin effectīvus (“productive; effective”), from efficiō (“to make; to bring about”), equivalent to effect + -ive.

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