1. performing or functioning in the best possible manner with the least waste of time and effort; having and using requisite knowledge, skill, and industry; competent; capable: a reliable, efficient assistant.
  2. satisfactory and economical to use: Our new air conditioner is more efficient than our old one.
  3. producing an effect, as a cause; causative.
  4. utilizing a particular commodity or product with the least waste of resources or effort (usually used in combination): a fuel-efficient engine.


  1. functioning or producing effectively and with the least waste of effort; competent
  2. philosophy producing a direct effect; causative

“capable of producing the desired effect,” late 14c., “making, producing immediate effect,” from Old French efficient and directly from Latin efficientem (nominative efficiens) “effective, efficient, producing, active,” present participle of efficere “work out, accomplish” (see effect). Meaning “productive, skilled” is from 1787. Related: Efficiently.

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