2
: beginning, commencement
the onset of winter
the onset of age-related diseases
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
During the onset of the COVID-19 pandemic, supply-chain disruptions contributed to a 25% spike in import prices (see chart).
—
Nick Sargen, Forbes.com, 14 July 2025
To Reveal Cancer Cells The Good Life: This Viral Pharmacist Says Sunscreen Isn't Enough This Summer
Psychedelic Drug May Slow Aging
In boys, sucralose stood out as the most significant sweetener associated with early puberty onset.
—Daniella Gray, MSNBC Newsweek, 13 July 2025
American kids also experienced an increase in early onset of menstruation, trouble sleeping, limitations in activity, physical symptoms, depressive symptoms and loneliness during the study period.
—Stephen Sorace, FOXNews.com, 8 July 2025
Throughout 2019, Chicago police officers made nearly 80,000 arrests before scaling them back significantly during the onset of the COVID-19 pandemic the following spring.
—Chicago Tribune, 30 June 2025
See All Example Sentences for onset
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Nick Sargen, Forbes.com, 14 July 2025
To Reveal Cancer Cells The Good Life: This Viral Pharmacist Says Sunscreen Isn't Enough This Summer
Psychedelic Drug May Slow Aging
In boys, sucralose stood out as the most significant sweetener associated with early puberty onset.
—Daniella Gray, MSNBC Newsweek, 13 July 2025
American kids also experienced an increase in early onset of menstruation, trouble sleeping, limitations in activity, physical symptoms, depressive symptoms and loneliness during the study period.
—Stephen Sorace, FOXNews.com, 8 July 2025
Throughout 2019, Chicago police officers made nearly 80,000 arrests before scaling them back significantly during the onset of the COVID-19 pandemic the following spring.
—Chicago Tribune, 30 June 2025
See All Example Sentences for onset
Cite this Entry
“Onset.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/onset. Accessed 21 Jul. 2025.
Copy CitationKids Definition
onset
noun
on·set
ˈȯn-ˌset 
ˈän-
Medical Definition
onset
noun
on·set
ˈȯn-ˌset, ˈän-
: the initial existence or symptoms of a disease
the onset of scarlet fever
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