From French effectif, from Latin effectīvus (productive; effective), from efficiō (I make; I bring about).



effective (comparative more effective, superlative most effective)

  1. Having the power to produce a required effect or effects.
    Synonym: efficacious
    The pill is an effective method of birth control.
  2. Producing a decided or decisive effect.
    The president delivered an effective speech!
    • 1651, Jer[emy] Taylor, The Rule and Exercises of Holy Living. [], 2nd edition, London: [] Francis Ashe [], →OCLC:
      Whosoever is an effective, real cause of doing his neighbour wrong, is criminal.
  3. Efficient, serviceable, or operative, available for useful work.
    How long does it take to make a bunch of civilians an effective military force?
    My effective income after taxes and child support is $500 a month.
    The effective radiated power is determined by multiplying the transmitter power output with the antenna gain.
    The effective voltage of an alternating current is 0.7 times its peak voltage.
    Antonym: nominal
  4. Actually in effect.
    The curfew is effective at midnight.
  5. (geometry, of a cycle or divisor) Having no negative coefficients.
  6. (physics, for any effective theory) approximate; Not describing the fundamental dynamic changes in some system as they happen.

Usage notesEdit

Webster's Revised Unabridged Dictionary from 1913 still lists efficient and effective as synonyms, but all major dictionaries now show that these words now only have different meanings in careful use. Use of both for the other meaning is however widespread enough that Longman's Exam Dictionary, for example, finds it necessary to proscribe the use of one for the other with several examples at each entry and provides the following summary:

  • efficient = working quickly and without waste
  • effective = having the desired effect

Derived termsEdit

Related termsEdit


The translations below need to be checked and inserted above into the appropriate translation tables. See instructions at Wiktionary:Entry layout § Translations.


effective (plural effectives)

  1. (military) a soldier fit for duty





  1. feminine singular of effectif




  1. vocative masculine singular of effectīvus