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

Ease regulations and improve supply Both Republican and Democratic candidates have proposed relief from regulations as a means of achieving greater efficiency, especially in the area of housing. — ABC News, 2 Nov. 2026

Rigid donor unlocks potential new designs Although laboratory organic solar cells have now surpassed 20% power conversion efficiency, researchers have continued searching for ways to reduce voltage losses while maintaining photocurrent. — Muskan Bhatia, Interesting Engineering, 2 Nov. 2026

That's a modest increase over the previous generation, but the bigger news is its improved battery efficiency and range. — New Atlas, 2 Nov. 2026

The defensive effort made Liberty’s red-zone efficiency even more frustrating. — Alejandro Hernandez, Miami Herald, 1 Nov. 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