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Synonyms

onset

American  
[on-set, awn-] / ˈɒnˌsɛt, ˈɔn- /

noun

  • onsets
    plural
  1. a beginning or start.

    the onset of winter.

  2. an assault or attack.

    an onset of the enemy.

  3. Phonetics. the segment of a syllable preceding the nucleus, as the gr in great.


onset British  
/ ˈɒnˌsɛt /

noun

  1. an attack; assault

  2. a start; beginning

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Word Forms

Noun Inflected Forms

Etymology

Origin of onset

1525–35; on + set, after the verb phrase set on

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.

Keep Reading on Vocabulary.com

Vocabulary lists containing onset

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.

See Examples For:

Jeffries was declared "mentally incompetent" by a court last year and said to be suffering with dementia and late onset of Alzheimer's disease.

From BBC Aug. 21, 2026

Burke insisted that new black lung cases do not reflect current mining conditions, because of the delay in the onset of symptoms.

From Barron's Aug. 21, 2026

Gross domestic product grew 0.2% in the second quarter, better than had been expected on the onset of the conflict in the Middle East.

From The Wall Street Journal Aug. 18, 2026

But so, too, was the onset of the COVID-19 pandemic, which sharply curtailed the Democratic nominating fight.

From Los Angeles Times Aug. 2, 2026

It appeared again with the onset of the rainy season but only flowed properly at its peak.

From "Flying Through Water" by Mamle Wolo

It is more common in women than men and typically onsets in 40s, often taking a significant toll on their quality of life.

From Science Daily Nov. 20, 2024

He and his colleagues analyzed 1952-2011 temperature data and found the four seasons no longer occur equally and had irregular onsets.

From Seattle Times Sep. 22, 2021

We used to call these “family words” when I was a kid: rat, bat, cat, mat, etc., all have the “-at” rime with different consonant onsets.

From Slate Nov. 29, 2018

Analyses of the passive playback experiments were the same as above, but the onsets and offsets of the sound sweeps were used as anchor points instead of the presses and the releases of the joystick.

From Nature Mar. 28, 2017

Weil's disease is characterized by sudden onsets of malaise, often intense muscular pain, high fever for several days, followed by jaundice, frequently accompanied by complications.

From Kelly Miller's History of the World War for Human Rights by Kelly Miller

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