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

Individuals are generally considered contagious several days before the onset of gland swelling and for about five days afterward. —Katia Hetter, CNN Money, 5 Mar. 2026

His tenure ended abruptly in April 2020, when he was fired—purportedly for cause—as the league suspended operations at the onset of the COVID-19 pandemic. —Daniel Libit, Sportico.com, 5 Mar. 2026

Lee also snapped a wide-angle shot of the moon as direct sunlight illuminated a thin crescent of its outer disk, mere minutes before the onset of totality, as the Beijing skyline stretched out below, pouring light into the night sky. —Anthony Wood, Space.com, 4 Mar. 2026

Their world shifts dramatically when Henry is diagnosed with early-onset Alzheimer’s. —Rosy Cordero, Deadline, 4 Mar. 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