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 the practical race in 2026 is won by mastering both contests at once with absolute capability and radical efficiency, closed excellence and open diffusion, the biggest reliable compute and the smartest use of it. — Mark Minevich, Fortune, 21 Aug. 2026

This efficiency means that researchers could potentially use the algorithm to help tackle other open problems in discrepancy theory, as well as questions in optimization theory, physics, finance, and more. — Quanta Magazine, 21 Aug. 2026

The Transit is powerful and has decent fuel efficiency for its size. — Charles Singh, USA Today, 21 Aug. 2026

Speed, efficiency, and safety are among the most crucial attributes of canal transport. — Scott Spires, Encyclopedia Britannica, 21 Aug. 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