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

Citroën/Stellantis The original 2CV was an extraordinary achievement of human engineering, balancing severe material shortages with unmatched spatial efficiency. — New Atlas, 12 Oct. 2026

Maia 300 will start being rolled out to production in 2027, and it has been designed with efficiency in mind. — Tom Warren, The Verge, 12 Oct. 2026

The efficiency gains mean longer-lasting batteries, with the iPhone 18 Pro Max winning a PCMag Lab Award for its record-setting longevity. — Eric Zeman, PC Magazine, 12 Oct. 2026

The Broncos need 4 yards per carry to improve early-down efficiency. — Troy Renck, Denver Post, 10 Oct. 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