on·​set | \ ˈȯn-ˌset How to pronounce onset (audio) , ˈän-\

Definition of onset

1 : attack, assault withstand the onset of the army
2 : beginning, commencement the onset of winter the onset of age-related diseases

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Examples of onset in a Sentence

the walls withstood the onset of the first battalion the claim that if you take enough vitamin C at the onset of a cold, you'll often recover faster

Recent Examples on the Web

Health officials in Indiana, Illinois, Oregon and Minnesota have also reported fatalities from sudden-onset illnesses that officials linked to vaping. Anchorage Daily News, "California man is seventh person to die from suspected vape-related illness," 17 Sep. 2019 That same month, doctors reported the first case of a sudden-onset, severe lung illness associated with vaping. Katherine Ellen Foley, Quartz, "Is it safe to vape?," 9 Sep. 2019 The worst long-term effect of excessive heat exposure would be death by heatstroke (especially from late-onset multi-organ failure and skin necrosis/slough that are secondary to heatstroke)! Maddie Hiatt, House Beautiful, "How To Keep Your Pet Safe This Summer," 26 July 2019 Other trials of anti-CD3 moved ahead in new-onset patients and were largely successful. Jennifer Couzin-frankel, Science | AAAS, "In milestone trial, experimental drug delays type 1 diabetes," 9 June 2019 Photo: mandel ngan/Agence France-Presse/Getty Images The Internet of Things Will Benefit Seniors Rick Phelps, founder of the online Alzheimer’s and dementia support group Memory People, was diagnosed with early-onset Alzheimer’s in 2010. Gary Shapiro, WSJ, "Hacking Health Care: How Tech Will Drive Down Costs," 6 Dec. 2018 Federer made his intentions known from the onset, coming in frequently and fruitfully on Evans’ slice backhand and limiting the errors that plagued him in those earlier matches. Daniel Rapaport, SI.com, "Federer, Serena Rounding Into Form Ahead U.S. Open's Second Week," 30 Aug. 2019 Mueller has repeatedly cited a Justice Department Office of Legal Counsel memo, which advises against the indictment of a sitting president, as something that from the onset of his probe made an indictment impossible. Allan Smith, NBC News, "Mueller pressed on how his inability to declare a crime took place doesn’t amount to an exoneration," 25 July 2019 Betty, 76, was one -- a partially blind and homeless woman suffering from the onset of dementia last fall. oregonlive.com, "Report: Hospital calls about ‘unwanted’ people trespassing leads to jail, criminalizing mental illness," 18 June 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'onset.' 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 onset

circa 1522, in the meaning defined at sense 1

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Statistics for onset

Last Updated

23 Sep 2019

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Time Traveler for onset

The first known use of onset was circa 1522

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More Definitions for onset



English Language Learners Definition of onset

: the beginning of something


on·​set | \ ˈȯn-ˌset How to pronounce onset (audio) , ˈän-\

Kids Definition of onset

1 : beginning sense 1 the onset of winter


on·​set | \ ˈȯn-ˌset, ˈän- How to pronounce onset (audio) \

Medical Definition of onset

: the initial existence or symptoms of a disease the onset of scarlet fever

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More from Merriam-Webster on onset

Rhyming Dictionary: Words that rhyme with onset

Thesaurus: All synonyms and antonyms for onset

Spanish Central: Translation of onset

Nglish: Translation of onset for Spanish Speakers

Britannica English: Translation of onset for Arabic Speakers

Comments on onset

What made you want to look up onset? Please tell us where you read or heard it (including the quote, if possible).


to spread over or through

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