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Synonyms

onset

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

noun

  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

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.

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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.

An Onset representative said the fraud committed by Patrick James “is simply staggering” and his “effort to recast himself as a victim and shift blame to Onset is nothing more than factually unsupported posturing.”

From The Wall Street Journal • Jan. 22, 2026

In 2022, one employee messaged another that the Onset employee who persuaded First Brands to take an inventory loan returning 179% would be the “employee of the year,” court papers show.

From The Wall Street Journal • Jan. 6, 2026

Onset says it is owed a further $1.9 billion.

From The Wall Street Journal • Jan. 6, 2026

They added that Onset is a “victim of the shocking fraud committed by Patrick James and his cohorts.”

From The Wall Street Journal • Jan. 6, 2026

From some, she got no answer: Onset; Mattapoisett; even Penikese, though it was the closest.

From "Beyond the Bright Sea" by Lauren Wolk