Definition
Suddenly; all at once. Used when something happens without warning or very quickly.
Example
急に雨が降り出した。
Show translation
It suddenly started to rain.
Etymology
From 急 (きゅう, *kyū*), a Sino-Japanese kanji meaning "urgent," "hasty," or "sudden," borrowed from Middle Chinese *kɨp*. The particle に (*ni*) converts the adjective into an adverb, a standard pattern in Japanese. The kanji 急 itself depicts haste and is shared across many East Asian languages (e.g., Mandarin 急 *jí*).
Cultural note
急に is extremely common in everyday Japanese speech and appears frequently in weather reports, news, and casual conversation. It pairs naturally with verbs of change: 急に寒くなった (it suddenly got cold), 急に静かになった (it suddenly went quiet). Be careful not to confuse 急に (suddenly) with 急いで (hurriedly/in a rush) — both come from 急 but carry subtly different nuances: 急に describes the unexpectedness of an event, while 急いで describes the speed of one's own action.