onset
n. uncountablen. the beginning of something, especially something unpleasant like a sickness or bad weather. You use it to talk about when a problem first starts to happen.
n. the initial stage or commencement of something, typically an adverse condition or event. Frequently used in medical contexts to describe the first appearance of symptoms.
The onset of winter brought heavy snow.
Early treatment is most effective if started immediately after the onset of symptoms.
The sudden onset of the economic crisis caught many investors off guard, leading to a rapid sell-off in global markets.
From on- + set. Compare Old English onsettan (“to impose; oppress, bear down”). For semantic parallels for the meaning to assault, compare cognate Russian насе́сть pf (naséstʹ), наседа́ть impf (nasedátʹ).
Typically used in the singular form, often following the definite article 'the'.