突然(とつぜん)に

Can be used with or without the に particle — both 突然(とつぜん) and 突然(とつぜん)に function as adverbs. The form without に is slightly more common in casual speech.

Common collocations

• 突然(とつぜん)に現(あらわ)れる: to appear suddenly
• 突然(とつぜん)に倒(たお)れる: to collapse suddenly
• 突然(とつぜん)に泣(な)き出(だ)す: to suddenly burst into tears
• 突然(とつぜん)の訪問(ほうもん): a sudden visit

Similar words

• 急(きゅう)に: suddenly — similar but often implies a change of state or speed
• いきなり: suddenly, without warning — more colloquial, emphasizes lack of preamble
• 不意(ふい)に: unexpectedly — literary, emphasizes catching someone off guard
• 唐突(とうとつ)に: abruptly — more formal, often about speech or behavior

Usage

突然(とつぜん) can also function as a な-adjective modifier: 突然(とつぜん)の知(し)らせ (a sudden notification).