1398, “making,” from Old French -, from Latin efficientem, nominative efficiēns, participle of efficere (see effect). Pronunciation
  • (RP) IPA: /ɪˈfɪʃənt/
  • (America, CA) IPA: /əˈfɪʃənt/


  1. making good, thorough, or careful use of resources; not consuming extra. Especially, making good use of time or energy
    An efficient process would automate all the routine work.
    Our cleaners are almost too efficient: they throw away anything left out on a desk.
  2. expressing the proportion of consumed energy that was successfully used in a process; the ratio of useful output to total input
    The motor is only 20% efficient at that temperature.
  3. causing effects, producing results; bringing into being; initiating change (rare except in philosophical and legal expression efficient cause = causative factor or agent)
    • It was well said of Plotinus, that the stars were significant, but not efficient.
    Ownership, maintenance, or use of the automobile need not be the direct and efficient cause of the injury sustained
  4. (proscribed, old use) effective
    • 1801, Robert Southey, Thalaba the Destroyer:
      Ye wake no more to anguish;‥ ye have borne
      The Chosen, the Destroyer!‥ soon his hand
      Shall strike the efficient blow;
      Soon shaking off your penal forms, shall ye,
      With songs of joy, amid the Eden groves,
      Hymn the Deliverer’s praise!
    • The efficient cause is the working cause.
Antonyms Translations Translations Translations Noun

efficient (plural efficients)

  1. (obsolete) a cause; something that causes an effect
    • 1643, Thomas Browne, Religio Medici, I.14:
      Some are without efficient, as God; others without matter, as Angels […].
    • This implies, that something happens without a cause. If it should be said, that motive in this case is not the efficient of the action or doing — this is granted; but at the same time, for reasons already given, it is denied, that the man himself is the efficient cause of it.

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