efficiency

noun

ef·​fi·​cien·​cy i-ˈfi-shən-sē 

plural efficiencies

1

: the quality or degree of being efficient

2

a

: efficient operation

b(1)

: effective operation as measured by a comparison of production with cost (as in energy, time, and money)

(2)

: the ratio of the useful energy delivered by a dynamic system to the energy supplied to it

3

: efficiency apartment

Synonyms of efficiency

• efficacy
• effectiveness
• efficaciousness

Examples of efficiency in a Sentence

Because of her efficiency, we got all the work done in a few hours.

The factory was operating at peak efficiency.

A furnace with 80 percent fuel efficiency wastes 20 percent of its fuel.

The company is trying to lower costs and improve efficiencies.

Recent Examples on the Web

But efficiency gains alone may not be enough to fix Renault’s worsening sales performance, which has contributed to a 20% slump in the share price this year. —Albertina Torsoli, Bloomberg, 9 Mar. 2026

Engineers believe the system could improve overall efficiency while reducing energy waste during operation. —Sujita Sinha, Interesting Engineering, 9 Mar. 2026

This configuration allows higher operating temperatures and improves thermal efficiency to about 41%, compared with roughly 31% for conventional reactors. —David Szondy march 08, New Atlas, 8 Mar. 2026

In a game where both teams shot 40% or less, Harrison and Shaw were able to find efficiency, both shooting above 45%. —Steven Johnson, Fort Worth Star-Telegram, 8 Mar. 2026

Word History

Etymology

borrowed from Latin efficientia, from efficient-, efficiens "producing or giving rise to something, immediate (of a cause), efficient" + -ia -y entry 2

First Known Use

1633, in the meaning defined at sense 1

Phrases Containing efficiency

• efficiency apartment
• efficiency expert
• hyper-efficiency

Rhymes for efficiency

• deficiency
• proficiency
• sufficiency
• immunodeficiency
• inefficiency
• insufficiency

Kids Definition

efficiency

noun

ef·​fi·​cien·​cy i-ˈfish-ən-sē 

plural efficiencies

1

: the quality or degree of being efficient

2

: efficient operation

3

: the ratio of the useful energy delivered by a machine to the energy supplied to it