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

Eco effort The Fontaine follows standard brand practices around linen reuse and energy efficiency, along with offering bulk bath amenities in the guest rooms. —Condé Nast, Condé Nast Traveler, 2 Mar. 2026

Adhere to local rules about water efficiency. —Elise Schmelzer, Denver Post, 1 Mar. 2026

Published in the journal Matter, the underlying mechanisms behind the inferior photochemical of polymer acceptor and develops a method to enhance both efficiency and stability through small-molecule incorporation. —Prabhat Ranjan Mishra, Interesting Engineering, 28 Feb. 2026

Dorsey tied the cuts directly to efficiency gains from the company’s AI rollout, Fortune reported. —Sheryl Estrada, Fortune, 28 Feb. 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