不意に|ふいにfuini

1. adverbsuddenly; abruptly; unexpectedly
   彼かれはふいに私わたしたちの話はなしに口くちをはさんだ。↗

   He interrupted us abruptly.

• SynonymいきなりCasualColloquial. Doing something right off the bat with no warning, as in 「いきなり殴る」; more abrupt than 「不意に」.
• Synonym突然とつぜんNeutralThe most common, neutral word for 'sudden'; objective in tone, as in 「突然の雨」. Also a noun or na-adjective.
• Synonym急きゅうNeutralNa-adjective, mostly used before nouns, as in 「急な話」; can mean sudden, or urgent and pressing, depending on context.
• Synonym突如とつじょWrittenWritten style with more force than 「突然」. For things erupting out of nowhere, as in 「突如現れる」.
• SynonymにわかにWrittenWritten. For something starting suddenly, as in 「にわかに雨が降り出す」; also 'not right away', as in 「にわかには信じがたい」.
• SynonymふとNeutralSudden but unintentional; focuses on thoughts or impulses that pop up unbidden, as in 「ふと思い出す」.
• Synonym急にきゅうにNeutralCommon in speech, as in 「急に寒くなる」; one of the general-purpose words for 'suddenly', alongside 「突然」.
• SynonymパッとNeutralIn a flash. Focuses on the instant an action occurs, as in 「パッと光る」.
• Synonym俄然がぜんNeutralDescribes something suddenly turning or intensifying, especially a sharp change of attitude, as in 「俄然やる気になる」.
• SynonymやにわにWrittenWritten and dated. Means doing something at once, without warning; stresses the abruptness of the action.
• SynonymふいとCasualColloquial. A sudden, offhand action in a single beat, as in 「ふいと立ち去る」.
• Synonym忽然こつぜんWrittenWritten. Typically describes something vanishing, as in 「忽然と消える」; the focus is on disappearance.
• Synonym思いがけずおもいがけずNeutralUnexpectedly, beyond what one imagined, as in 「思いがけず再会した」; stresses that the outcome defies expectations.
• SynonymふっとNeutralSudden but slight and momentary, as in 「ふっと笑う」; focuses on a brief flicker of action.
• SynonymついとNeutralQuick and brisk, as in 「ついと去る」; rarely used, and focuses on the light, swift motion.
• Related急激きゅうげきNeutralNa-adjective for drastic, sharp change, as in 「急激な変化」; stresses the magnitude of the change, not that it was unexpected.
• RelatedとみにWrittenWritten. Means markedly, noticeably more, as in 「頓に増えた」; it does not carry any sense of the unexpected.

Use 「不意に」 when something happens while you are off guard, as in 「不意に声をかけられた」. For the general idea of 'suddenly', pick 「突然」 or, in speech, 「急に」; for an action that comes with no warning at all, 「いきなり」. 「突如」 is a stronger written option, 「急激」 is for drastic change, and 「ふと」 for thoughts that pop up unbidden.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 予想よそうしないで、急きゅうに起おこる様子ようす。