on·​set | \ˈȯn-ˌset, 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

Many of the works that Ms. Gubar cites reflect her own situation and focus on newer, late-onset love as opposed to decadeslong unions. Heller Mcalpin, WSJ, "‘Late-Life Love’ Review: The Glow at Sunset," 22 Nov. 2018 And her openness about late-onset postpartum depression has helped shed light on an issue that too often goes undiscussed. Jessica Pressler, Glamour, "Chrissy Teigen Is the Unofficial Voice of Generation Fed Up," 1 Nov. 2018 After the diagnosis of his mom, Suzy, with early-onset Alzheimer’s in 2014, Bishop started the 4MOM Charity while at the University of Washington and has worked tirelessly to bring awareness of this disease that has affected both him and his family. Ryan Divish, The Seattle Times, "Mariners announce 2018 minor league award winners," 25 Sep. 2018 On Thursday, the 21-year-old model showed off two snaps of herself onset rocking a surprising new hair color: electric-blue. Melody Chiu, PEOPLE.com, "Hailey Baldwin Shows Off Electric-Blue Hair in Sexy Mirror Selfie," 7 June 2018 In rapid onset emergencies, mapping often isn’t as high of a priority as basic necessities like food, water and shelter. Brian Tomaszewski, Smithsonian, "Teaching Refugees How To Map Their World Could Have Huge Benefits," 22 May 2018 The next whitelash came at the onset of the civil rights and black liberation movement of the 1950s, 1960s, and 1970s, when an intense and significant mobilization of black people saw an equally intense backlash. Kim Reynolds, Teen Vogue, "How White People Have Reacted to Black Success Over Time in the United States," 30 July 2018 Since the onset of austerity, local and central government have driven ever-harder deals with their contractors. The Economist, "Britain’s outsourcing model, copied around the world, is in trouble," 28 June 2018 Evidence of the ways neural tissue is partially destroyed after a stroke or the onset of dementia has been around for decades. Susan Pinker, WSJ, "New Skills Build New Brain Architecture, Research Shows," 14 June 2018

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

2 Dec 2018

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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, ˈän-\

Kids Definition of onset

1 : beginning sense 1 the onset of winter


on·​set | \ˈȯn-ˌset, ˈän- \

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).


living or existing for a long time

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