How to say "uncertain" in Japanese

• 不定ふていCommon
  no-adjective, na-adjectiveUsed when something is unsettled, indefinite, or unfixed — a schedule, date, or status that has not been decided. The nuance is that no definite form or determination has been reached, rather than doubt about truth.
• 疑わしいうたがわしいCommon
  i-adjectiveCovers the doubtful or questionable sense of 'uncertain': something whose truth, honesty, or validity is in dispute. It carries suspicion, so it fits claims, evidence, or alibis you are not sure you can believe.
  彼かれが時間じかんどおり来くるかどうかは疑うたがわしいと思おもう。↗

  I doubt if he will come on time.
• あやふやJLPT N1approx.Common
  na-adjectiveA mimetic word for the vague, ambiguous sense of 'uncertain' — fuzzy memories, half-hearted answers, or feelings you cannot pin down. It suggests instability and lack of clarity rather than a formal judgment.
  あやふやな手てつきで一いち枚まいの紙かみを動うごかした。↗

  She fumbled with a piece of paper.
• 不確実ふかくじつCommon
  na-adjective, nounFor the uncertain in the sense of unreliable, insecure, or not guaranteed — future prospects, plans, or outcomes that may not hold. The nuance is risk about what will actually happen or whether something can be depended on.
  ネット上じょうの不ふ確実かくじつな情報じょうほうを鵜呑うのみにしてはならない。↗

  You mustn't swallow unreliable information that's on the Web.
• 不確定ふかくていCommon
  na-adjective, nounClose to 不定: something indefinite or not determined, such as terms, conditions, or values left open. It often appears in more formal or technical contexts where a precise determination has not been made.

Choose 不定 or 不確定 for things not fixed or determined, 「疑わしい」 for doubtful or questionable matters, 「あやふや」 for vague, ambiguous impressions, and 不確実 for unreliable, insecure outcomes.

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

• 不定ふていunsettled
• 疑わしいうたがわしいdoubtful
• あやふやuncertain
• 不確実ふかくじつuncertain
• 不確定ふかくていuncertain
• 不確かふたしかunreliable
• 不明ふめいunclear
• 危なっかしいあぶなっかしいdangerous
• おぼつかないuncertain
• 定めないさだめないuncertain
• 生半なまなかhalfway-done
• 火宅無常かたくむじょうimpermanent (like a burning house)
• 未確定みかくていunconfirmed
• 危なかしいあぶなかしいdangerous
• 危ないあぶないuncertain
• 怪しいあやしいdoubtful
• 混沌こんとんchaotic
• 無常むじょうmutable
• 不透明ふとうめいunclear
• 危ういあやういprecarious (situation)