break·​through | \ ˈbrāk-ˌthrü How to pronounce breakthrough (audio) \
plural breakthroughs

Definition of breakthrough

 (Entry 1 of 2)

1a : a sudden advance especially in knowledge or technique a medical breakthrough
b : a person's first notable success often used before another noun a breakthrough novelthe actress's breakthrough performance
2a : an act or instance of moving through or beyond an obstacle a breakthrough in the talks between the region's leaders a breakthrough agreement
b : an instance of passing through a barrier or protection The ice under the surface begins to deteriorate, increasing the risk of breakthroughs.— Vicki Winger specifically, medical : infection occurring in someone who is fully vaccinated against an infectious agent A vaccine breakthrough occurs when a person tests positive for COVID-19 two weeks after being fully vaccinated against the disease … — David Rasbach often used before another noun Two other CDC studies of breakthrough cases at nursing homes showed the vaccines protected residents, even when the virus spread through the homes. — Maura Dolan … the academy recently recommended that children receive two doses of the chicken pox vaccine, rather than just one, because the additional dose bolsters immunity and may help reduce breakthrough infection. — Maria Raven
3 warfare : an offensive military assault that penetrates and carries beyond a defensive line

break through

broke through; broken through; breaking through; breaks through

Definition of break through (Entry 2 of 2)

intransitive verb

: to make a breakthrough

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Synonyms & Antonyms for breakthrough

Synonyms: Noun

Antonyms: Noun

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Examples of breakthrough in a Sentence

Noun Researchers say they have made a major breakthrough in cancer treatment. The police have announced a breakthrough in the murder case. This job could be the breakthrough she's been waiting for.
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Recent Examples on the Web: Noun Last week, pro Cheryl Burke and her partner Cody Rigsby tested positive for breakthrough cases. Dory Jackson,, 5 Oct. 2021 However, with the Delta variant still spreading, and because breakthrough cases are most dangerous to the elderly and immunocompromised, lockdowns have not entirely ended for many nursing homes. Lila Maclellan, Quartz, 4 Oct. 2021 And some people who have been vaccinated have gotten breakthrough cases, though that number is seen to be relatively small. Catherine Ho, San Francisco Chronicle, 1 Oct. 2021 Just 11% of vaccinated people thought breakthrough cases indicate the vaccines aren’t working, Kaiser found, and 19% thought the same of booster shots. Robert Hart, Forbes, 28 Sep. 2021 As of July 19, there were 1,141 deaths attributed to these breakthrough cases reported to the CDC out of 161 million people vaccinated. Lois K. Solomon,, 27 Sep. 2021 Oddly enough, counting the number of breakthrough cases, hospitalizations and deaths — times the vaccine didn’t work — is a really effective way of telling the story of just how well the vaccine does its job. Andy Larsen, The Salt Lake Tribune, 25 Sep. 2021 Now, in the age of booster shots and breakthrough cases, the phrase has gotten even murkier. Rachel Gutman, The Atlantic, 24 Sep. 2021 Osterholm pointed out that, in Minnesota, where vaccination rates are high, breakthrough cases already represent a third of all cases. The New Yorker, 23 Sep. 2021

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'breakthrough.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of breakthrough


1915, in the meaning defined at sense 3


1946, in the meaning defined above

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Time Traveler for breakthrough

Time Traveler

The first known use of breakthrough was in 1915

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Dictionary Entries Near breakthrough

break through


break time

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Statistics for breakthrough

Last Updated

9 Oct 2021

Cite this Entry

“Breakthrough.” Dictionary, Merriam-Webster, Accessed 15 Oct. 2021.

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More Definitions for breakthrough



English Language Learners Definition of breakthrough

: a sudden increase in knowledge, understanding, etc. : an important discovery that happens after trying for a long time to understand or explain something
: a person's first important success


break·​through | \ ˈbrāk-ˌthrü How to pronounce breakthrough (audio) \

Kids Definition of breakthrough

: a sudden advance or successful development a breakthrough in medical research

More from Merriam-Webster on breakthrough

Nglish: Translation of breakthrough for Spanish Speakers

Britannica English: Translation of breakthrough for Arabic Speakers Encyclopedia article about breakthrough


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