onset

noun

on·​set ˈȯn-ˌset 

ˈän-

1

: attack, assault

withstand the onset of the army

2

: beginning, commencement

the onset of winter

the onset of age-related diseases

Synonyms of onset

• attack
• assault
• onslaught
• raid
• offensive
• aggression
• offense
• strike

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

After the age of, say, 45, anyone might start forgetting names, misplacing items, or struggling to pay attention, and the onset of such symptoms can often prompt a visit to a doctor, if only to confirm a patient’s hunch that the passage of time is to blame. —Yasmin Tayag, The Atlantic, 25 Feb. 2026

More is being learned about the onset of menstruation, preeclampsia in pregnancy, and the impact of menopause than what was taught in medical school 25 years ago, Joynt Maddox said. —Elizabeth Cooney, STAT, 25 Feb. 2026

In just one week, a spectacular display of orbital mechanics will be visible to billions of people across the Americas, Asia, and Oceania, as Earth's shadow sweeps across the lunar disk, triggering the onset of an awe-inspiring 'blood moon' total lunar eclipse. —Daisy Dobrijevic, Space.com, 24 Feb. 2026

Major Arctic wildland fires delay the onset of snow cover by five days, offshore wind farms in the northern Yellow Sea stabilize ecosystems, and microplastics inhibit oceanic carbon uptake. —Rafil Kroll-Zaidi, Harpers Magazine, 24 Feb. 2026

Word History

First Known Use

circa 1522, in the meaning defined at sense 1

Phrases Containing onset

• adult-onset diabetes
• juvenile-onset diabetes

Rhymes for onset

• abet
• asset
• baguette
• banquette
• barbette
• beget
• beset
• brevet
• briquette
• brunet
• brunette
• burette

Kids Definition

onset

noun

on·​set ˈȯn-ˌset 

ˈän-

1

: attack entry 2 sense 1

2

: beginning sense 1

Medical Definition

onset

noun

on·​set ˈȯn-ˌset, ˈän- 

: the initial existence or symptoms of a disease

the onset of scarlet fever