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

The foundation model market is increasingly resembling an infrastructure industry, where scale, capital, and operational efficiency are paramount for dominant players. — Gerui Wang, Forbes.com, 1 Aug. 2026

Although official specifications remain classified, analysts believe improved endurance and fuel efficiency will be among the aircraft’s key advantages. — Prabhat Ranjan Mishra, Interesting Engineering, 31 July 2026

Now the question is whether Tiley can stimulate another level of success for the USTA, a fragmented organization with a mixed reputation for efficiency. — Matthew Futterman, New York Times, 31 July 2026

But the platform designation was designed to increase efficiency and speed the path of treatments. — Kat Bryant Knudson, STAT, 31 July 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