2
: beginning, commencement
the onset of winter
the onset of age-related diseases
Synonyms of onset
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
The selloff amounted to the biggest one-day decline in markets since the onset of the COVID-19 pandemic.
—
Max Zahn, ABC News, 31 Dec. 2025
Classmate Kamryn McElvain completed the scoring in the first minute of the second half during the onset of sprinkles that persisted the rest of the way.
—Glae Thien, San Diego Union-Tribune, 31 Dec. 2025
At the onset of the year, the world’s second-largest economy was left for dead.
—Shuli Ren, Twin Cities, 30 Dec. 2025
Pigsqueak With the onset of cold temperatures, the green foliage of pigsqueak (Bergenia cordifolia) turns brilliant shades of maroon.
—Megan Hughes, Better Homes & Gardens, 28 Dec. 2025
See All Example Sentences for onset
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Max Zahn, ABC News, 31 Dec. 2025
Classmate Kamryn McElvain completed the scoring in the first minute of the second half during the onset of sprinkles that persisted the rest of the way.
—Glae Thien, San Diego Union-Tribune, 31 Dec. 2025
At the onset of the year, the world’s second-largest economy was left for dead.
—Shuli Ren, Twin Cities, 30 Dec. 2025
Pigsqueak With the onset of cold temperatures, the green foliage of pigsqueak (Bergenia cordifolia) turns brilliant shades of maroon.
—Megan Hughes, Better Homes & Gardens, 28 Dec. 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 5 Jan. 2026.
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
Love words? Need even more definitions?
Merriam-Webster unabridged
Share