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

Shaw is one of the best strikers in the world, with a profound aerial efficiency in both boxes. —Megan Feringa, New York Times, 31 May 2026

The chaos on the Republican side was matched by efficiency and a show of force on the DFL side. —Esme Murphy, CBS News, 31 May 2026

Carriers often became obsessed with speed and efficiency. —Peter Hessler, New Yorker, 31 May 2026

Trimble praised the efficiency and structure of the workout, which was his second with an NBA team. —Tony East, Forbes.com, 31 May 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