How to say "improbable" in Japanese

• なさそうCommon
  suffix, na-adjectiveThe everyday sense: something does not seem likely to happen or be true. It is the common choice — use it when you are saying that something looks unlikely, an impression rather than a stated probability.
  「宝たからくじでも買かう？」「俺おれ、ギャンブル運うんとか無なさそうだしなぁ」↗

  "Buy a lottery ticket or something?" "Well, I don't think I've got much luck with gambling."
• ありそうもない
  expressionCovers 'improbable; unlikely': use it for something you judge to have little chance of being true or happening. A less common alternative to なさそう for this judgment, usually written in kana.
• 可能性が低いかのうせいがひくい
  expression, i-adjectiveSays directly that the possibility of something is low. Use it when you are talking about likelihood itself — how probable an outcome is — rather than an impression; less common than なさそう.
• 可能性の低いかのうせいのひくい
  expression, i-adjectiveThe same statement of low likelihood as 可能性が低い, with の in place of が; the difference is phrasing rather than meaning, and it is likewise less common than なさそう.
• まずない
  expression, i-adjectiveCovers 'very unlikely (to happen)': really a 'hardly ever' word, about events that practically never occur. For plain 'improbable' it overstates the case; use it only when you mean the chance is close to nil.
  彼かれは映画館えいがかんに行いくことはまずない。↗

  He seldom, if ever, goes to the cinema.

Use 「なさそう」, the common word, when something does not seem likely; 「ありそうもない」 when you state that it is improbable; 「可能性が低い」 and 「可能性の低い」 when you frame it as low likelihood; 「まずない」 when it almost never happens.

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

• なさそうdoes not seem
• ありそうもないimprobable
• 可能性が低いかのうせいがひくいunlikely
• 可能性の低いかのうせいのひくいunlikely
• まずないvery rare