efficiency

noun

ef·​fi·​cien·​cy i-ˈfi-shən-sē How to pronounce efficiency (audio)
plural efficiencies
Synonyms of efficiency
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

Relevance
See All Synonyms & Antonyms in Thesaurus

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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
And across the country, utilities have blocked energy-efficiency programs and kept independent storage projects waiting in line for years to connect to the grid. — Joshua MacEy, Hartford Courant, 28 Aug. 2026 In an interview with CNBC, OpenAI CEO Sam Altman emphasized the efficiency gains of the Sol model. — CNBC, 28 Aug. 2026 Traditional cement production typically runs at only 30 to 40 percent thermal efficiency. — Georgina Jedikovska, Interesting Engineering, 27 Aug. 2026 The new tower will be about 50 feet taller than the existing structure and will feature modern technologies designed to improve visibility, communications, operational efficiency and safety for air traffic controllers and airport users. — Carole Carlson, Chicago Tribune, 27 Aug. 2026 See All Example Sentences for efficiency

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

Time Traveler
The first known use of efficiency was in 1633

Phrases Containing efficiency

Rhymes for efficiency

See All Rhymes for efficiency

Browse Nearby Words

efficience
efficiency
efficiency apartment
See all Nearby Words

Cite this Entry

“Efficiency.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/efficiency. Accessed 1 Sep. 2026.

Copy Citation

Kids Definition

efficiency

noun
ef·​fi·​cien·​cy i-ˈfish-ən-sē How to pronounce efficiency (audio)
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

More from Merriam-Webster on efficiency

Britannica.com: Encyclopedia article about efficiency

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Popular in Grammar & Usage

See More

A Who’s Who Regarding ‘Who’s’ and ‘Whose’

Is it 'nerve-racking' or 'nerve-wracking'?

What's the difference between 'fascism' and 'socialism'?

Why does English have so many silent letters?

7 Pairs of Commonly Confused Words
See More

Popular in Wordplay

See More

Ye Olde Nincompoop: Old-Fashioned Words for 'Stupid'

14 Phobias You Probably Haven't Heard Of

Even More Words That Sound Like Insults But Aren't

Even More Bird Names that Sound Like Insults (and Sometimes Are)

12 Lovely and Unusual Words for the Natural World
See More

Popular

See More

A Who’s Who Regarding ‘Who’s’ and ‘Whose’

Ye Olde Nincompoop: Old-Fashioned Words for 'Stupid'

14 Phobias You Probably Haven't Heard Of
See More

Games & Quizzes

See All
Play Quordle: Guess all four words in a limited number of tries. Each of your guesses must be a real 5-letter word.
Quordle Can you solve 4 words at once?
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.
Blossom Pick the best words!
Play Missing Letter: a crossword with a twist. Each of the 25 puzzle words start with a different letter of the alphabet. Which letter is missing?
The Missing Letter A daily crossword with a twist
skateboard-dog-hat
Wordmaxxing Slang Quiz Give your vocabulary a glow up by getting sendy w...
See All