ふと・不図・不斗futo

1. adverbsuddenly; casually; accidentally; incidentally; unexpectedly; unintentionally
   彼かれはそれを見みるとふと魔まがさして盗ぬすんだ。↗

   The sight tempted him to steal.

• SynonymたまたまNeutralRefers to things happening by chance or coincidence, as in 「たまたま会った」; 「ふと」 is about thoughts or actions occurring unintentionally.
• Synonym偶然ぐうぜんNeutralA noun and adjectival noun for coincidence or chance; 「ふと」 is an adverb focused on the unintentional.
• Synonym不意にふいにNeutralStresses being caught off guard, as in 「不意に声をかけられる」; 「ふと」 leans toward inner, unintentional thoughts.
• SynonymついNeutralIn spite of yourself, unable to resist, as in 「つい食べすぎた」 or 「つい笑顔になる」; 「ふと」 is about the unintentional.
• SynonymパッとCasualA mimetic word for something happening in a flash or spreading at once; 「ふと」 is about the unintentional.
• Synonym何気なくなにげなくNeutralDoing something casually or as if nothing were happening, as in 「何気なく見る」; 「ふと」 is about a thought suddenly occurring.
• Synonym急にきゅうにNeutralSuddenly or abruptly, often modifying changes; 「ふと」 is about unintentional thoughts.
• SynonymたまさかWrittenWritten/formal prose with an archaic flavor, meaning by chance or rarely; in everyday speech use 「たまたま」.
• Synonym思いがけずおもいがけずNeutralStresses that the outcome is unexpected, as in 「思いがけず再会した」; 「ふと」 focuses on subconscious thoughts or actions.
• Synonym図らずもはからずもWrittenNot a true antonym: it likewise means unexpected and unforeseen, in written/formal prose and often as a humble expression; 「ふと」 is about unintentional thoughts.
• SynonymふいとNeutralColloquial; someone casually and suddenly does something, as in 「ふいと立ち去る」; 「ふと」 more often modifies thoughts or one's gaze.
• SynonymふっとNeutralColloquial; unintentionally or in an instant, and it can describe blowing air; very close to 「ふと」 but with a stronger sense of the instant.
• SynonymゆくりなくWrittenWritten/formal prose and archaic, meaning unexpectedly; in daily speech say 「思いがけず」.
• SynonymひょいとCasualColloquial; a light, quick movement or doing something casually, as in 「ひょいと顔を出す」; 「ふと」 leans toward thoughts.
• SynonymはしなくもWrittenWritten/formal prose for unexpectedly or by coincidence; in daily speech say 「たまたま」.
• Synonym期せずしてきせずしてWrittenWritten/formal prose for what was never anticipated, often in 「期せずして一致した」; 「ふと」 is more colloquial.
• SynonymついとNeutralA quick, light movement, with a literary flavor; 「ふと」 more often modifies thoughts.
• SynonymはたとNeutralMostly in 「はたと気づく」 or 「はたと困る」, for realizing or being stumped all at once; 「ふと」 is lighter in feel.
• RelatedなんとなくNeutralFor no reason you can name, vaguely, as in 「なんとなく寂しい」; 「ふと」 is about a momentary thought.
• RelatedさっとNeutralA brisk, deft action, or wind and rain arriving suddenly; 「ふと」 is about the unintentional.
• RelatedいきなりNeutralColloquial; acting suddenly with no lead-up; 「ふと」 is about the unintentional.
• Related急激きゅうげきNeutralAn adjectival noun for changes that are rapid and sharp, modifying the change itself; 「ふと」 is an adverb for thoughts or actions happening suddenly or by chance.
• Related思わずおもわずNeutralInvoluntarily or despite yourself, as in 「思わず笑った」; 「ふと」 is about a thought occurring by chance.
• RelatedつとWrittenWritten/formal and old-fashioned, for rising or moving abruptly; rarely used in modern Japanese.
• RelatedばっとCasualA mimetic word for a sudden, vigorous movement or rapid spreading; 「ふと」 is about thoughts.

Use 「ふと」 when a thought comes to you or you notice something unintentionally. For things happening by coincidence, choose 「たまたま」 or 「偶然」. For acting in spite of yourself, use 「思わず」; for slipping up without meaning to, 「つい」. When the result is unexpected, say 「思いがけず」. In written/formal prose, 「図らずも」 covers unexpected outcomes, often humbly. Mimetic words like 「パッと」 and 「ばっと」 stress sudden motion, 「不意に」 being caught off guard, and 「何となく」 vague feelings with no clear reason.

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

1. （「はからず」にも当あてる）思おもいがけず、図はからずも。
2. （和語わご「ふと」に当あてる）突然とつぜん、にわかに、たまたま。