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Synonyms

efficiency

American  
[ih-fish-uhn-see] / ɪˈfɪʃ ən si /

noun

plural

efficiencies

  1. the state or quality of being efficient, or able to accomplish something with the least waste of time and effort; competency in performance.

  2. accomplishment of or ability to accomplish a job with a minimum expenditure of time and effort.

    The assembly line increased industry's efficiency.

  3. the ratio of the work done or energy developed by a machine, engine, etc., to the energy supplied to it, usually expressed as a percentage.

  4. efficiency apartment.

efficiency British  
/ ɪˈfɪʃənsɪ /

noun

  1. the quality or state of being efficient; competence; effectiveness

  2. the ratio of the useful work done by a machine, engine, device, etc, to the energy supplied to it, often expressed as a percentage See also thermal efficiency

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
efficiency Scientific  
/ ĭ-fĭsh′ən-sē /

  1. The ratio of the energy delivered (or work done) by a machine to the energy needed (or work required) in operating the machine. The efficiency of any machine is always less than one due to forces such as friction that use up energy unproductively.

  2. See also mechanical advantage

  3. The ratio of the effective or useful output to the total input in any system.

Other Word Forms

  • nonefficiency noun
  • superefficiency noun

Etymology

Origin of efficiency

First recorded in 1585–95; from Latin efficientia, from efficient- (stem of efficiēns efficient ) + -ia -y 3

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

This approach maximizes bandwidth efficiency and adapts to changes in signal quality.

From Science Daily • Apr. 2, 2026

He instead argued that the speed at which commanders are now taking action is a "consequence of the increased efficiency" that Maven has enabled.

From BBC • Apr. 1, 2026

Irenic proposed staff cuts, shelving projects, and leveraging AI; Snap’s board welcomes input, focusing on efficiency.

From Barron's • Mar. 31, 2026

Meanwhile, improved fuel efficiency means that people aren’t pumping as much gasoline as before.

From The Wall Street Journal • Mar. 31, 2026

Every time that an animal eats a plant or another animal, the conversion of food biomass into the consumer’s biomass involves an efficiency of much less than 100 percent: typically around 10 percent.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.