onset
Americannoun
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a beginning or start.
the onset of winter.
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an assault or attack.
an onset of the enemy.
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Phonetics. the segment of a syllable preceding the nucleus, as the gr in great.
noun
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an attack; assault
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a start; beginning
Etymology
Origin of onset
Compare meaning
How does onset compare to similar and commonly confused words? Explore the most common comparisons:
Explanation
When something is at its onset, it's at the beginning, just getting started, and it's often something that's not so pleasant. The onset of hurricane season is probably not the best time to visit the beach. If you catch an infection right at the onset and treat it immediately, the infection may not last so long. You can also have an early onset of something, and that usually means something you'd rather not have at all, as with early-onset Alzheimer's, a disease that usually appears after age 65. If you begin showing signs of the disease at a younger age than usual, you're said to have early-onset Alzheimer's.
Vocabulary lists containing onset
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
“Early onset breast cancer” — diagnosed before age 50 — “is going up the fastest among Asian Americans,” Gomez said.
From Los Angeles Times • Jun. 6, 2026
Mexico reported 1,717 active cases as of early May, while Panama’s caseload has grown so severe since its 2023 onset that officials have abandoned individual case tracking.
From Barron's • Jun. 4, 2026
The study found that a one year course of the biologic drug abatacept significantly delayed the onset of rheumatoid arthritis, with benefits continuing long after treatment ended.
From Science Daily • Jun. 1, 2026
Many oil-market analysts at the onset of the U.S.-Iran war said the global economy would start to feel the pinch of a virtually shut Strait of Hormuz as early as May.
From MarketWatch • May 26, 2026
It was a relief not to be writing out the she saids, or describing the weather or the onset of spring or her heroines face—beauty, she had discovered, occupied a narrow band.
From "Atonement" by Ian McEwan
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
