How to say "undoubtedly" in Japanese

• きっとJLPT N4approx.Common
  adverbCovers 'undoubtedly' as confident conjecture: the speaker strongly expects something and judges it almost certain — around ninety percent likely — rather than known for a fact. Typical when predicting outcomes or drawing inferences.
  でもよー、オラのおとうさんは良よい気きしねーよ、きっと。↗

  But I don't think Dad would like me to.
• 大丈夫だいじょうぶJLPT N5approx.Common
  adverbPrimarily means 'all right; fine; no problem', so as 'undoubtedly' it fits reassuring assertions that something will certainly be fine; for confident conjecture in general it is seldom the word you want.

Use 「きっと」 for 'undoubtedly' as confident conjecture — something judged almost certain rather than known for a fact — and reserve 大丈夫 for the reassuring sense that something will certainly be all right.

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

• きっとsurely
• まさしくcertainly
• 紛う方なくまごうかたなくundoubtedly
• 大丈夫だいじょうぶcertainly