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

What technology breakthroughs will underpin this forecasted dramatic improvement in the resource efficiency of artificial intelligence? — Rob Toews, Forbes.com, 22 June 2026

The aircraft is expected to compete in the ultra-long-range segment, serving customers who require intercontinental travel with enhanced efficiency and luxury. — Prabhat Ranjan Mishra, Interesting Engineering, 21 June 2026

There is also an efficiency problem. — New Atlas, 21 June 2026

This can minimize cooling efficiency by making the unit work harder to bypass the clog, cause water damage from an overflowing drain pan, and even trigger respiratory issues from mold and mildew growth. — Quincy Bulin, Southern Living, 21 June 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