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[ih-fish-uh n-see] /ɪˈfɪʃ ən si/
noun, plural efficiencies.
the state or quality of being efficient, or able to accomplish something with the least waste of time and effort; competency in performance.
accomplishment of or ability to accomplish a job with a minimum expenditure of time and effort:
The assembly line increased industry's efficiency.
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.
Origin of efficiency
1585-95; < Latin efficientia, equivalent to efficient- (see efficient) + -ia -y3
Related forms
nonefficiency, noun
superefficiency, noun, plural superefficiencies. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for efficiency
Contemporary Examples
Historical Examples
  • Much of the efficiency of the motor is due to the form and gearing of the propeller.

    Flying Machines W.J. Jackman and Thos. H. Russell
  • He has discharged the duties of this office for four years with ability and efficiency.

  • You've pictured one spot of efficiency in a whole dreary desert of waste.

    The Harbor Ernest Poole
  • And by degrees I made for myself a new god, and its name was efficiency.

    The Harbor Ernest Poole
  • That's more important to you and me than all the efficiency gods on earth.

    The Harbor Ernest Poole
British Dictionary definitions for efficiency


noun (pl) -cies
the quality or state of being efficient; competence; effectiveness
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
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Word Origin and History for efficiency

1590s, "power to accomplish something," from Latin efficientia (from efficientem; see efficient) + -cy. In mechanics, "ratio of useful work done to energy expended," from 1858. Attested from 1952 as short for efficiency apartment (itself from 1930).

Online Etymology Dictionary, © 2010 Douglas Harper
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efficiency in Medicine

efficiency ef·fi·cien·cy (ĭ-fĭsh'ən-sē)

  1. The production of the desired effects or results with minimum waste of time, effort, or skill.

  2. A measure of effectiveness; specifically, the useful work output divided by the energy input in any system.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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efficiency in Science
  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. See also mechanical advantage.

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

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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