noun, plural ef·fi·cien·cies.

  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.

noun plural -cies

  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 percentageSee also thermal 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).


  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.

  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.
58 queries 0.537