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

Controlling dust and allergies is a big reason, as well as increasing the HVAC efficiency, too. —Daley Quinn, Southern Living, 29 Nov. 2025

The system also required far fewer training samples—achieving high performance with just 40 examples, compared to 200 needed by baseline models—demonstrating strong efficiency and adaptability. —Jijo Malayil, Interesting Engineering, 28 Nov. 2025

If efficiency is your priority during this busy time of year, our list of easy cookie recipes is here for you. —Zoe Denenberg, Bon Appetit Magazine, 28 Nov. 2025

This tension between efficiency and inspiration now defines retail’s next frontier. —Cecile Van Steenberge, Fortune, 28 Nov. 2025

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