不確定|ふかくていfukakutei

1. na-adjective, noununcertain; indefinite

• Synonym未定みていNeutralFor things not yet decided, especially schedules and plans, as in 「日程は未定」. More everyday and common than 「不確定」.
• Synonym不定ふていWrittenWritten/formal prose. For things not fixed, as in 「住所不定」「不定期」. Stresses lacking any set pattern rather than awaiting a decision.
• Synonym不確かふたしかNeutralColloquial. For unreliable or hard-to-recall matters, as in 「不確かな記憶」. Focuses on trustworthiness rather than pending settlement.
• SynonymあやふやNeutralColloquial. For vague, unreliable matters, mainly memories and accounts; close to 「不確か」.
• Synonym不確実ふかくじつWrittenWritten/formal prose. For uncertainty carrying risk, as in 「不確実性」. Leans toward prediction and judgment.
• Synonym未確定みかくていNeutralNearly synonymous with 「不確定」; suggests a procedure has not yet run its course. Used for things not yet confirmed.
• Synonym未決定みけっていNeutralFor something not yet decided, focusing on the decision-making process. A bit more formal than 「未定」.
• Related不明ふめいNeutralFor something unclear or unknown, as in 「原因不明」. Focuses on missing information; can also describe a murky situation that cannot be determined.
• Related曖昧あいまいNeutralFor vague, ambiguous attitudes and expressions, and for policies or conclusions not clearly settled. Focuses on indistinctness.
• RelatedうやむやNeutralFor handling something vaguely and letting it slide, as in 「うやむやにする」. Focuses on the way it is dealt with, often implying it is dropped.
• Related未解決みかいけつNeutralFor problems or cases not yet solved, as in 「未解決の課題」「未解決事件」. Stresses that resolution is still awaited.
• Related不安定ふあんていNeutralFor unstable states, as in 「情緒不安定」. Focuses on fluctuation, not on something not yet settled.
• Related疑わしいうたがわしいNeutralFor something doubtful or questionable, focusing on truthfulness. Not used for matters still awaiting decision.
• Related怪しいあやしいNeutralColloquial. For something suspicious or unreliable; also of weather about to turn, as in 「雲行きが怪しい」.
• Related不鮮明ふせんめいWrittenWritten/formal prose. For indistinct images and also 「態度が不鮮明」. Centers on being hard to see or make out.
• Related宙ぶらりんちゅうぶらりんCasualColloquial. For something left hanging and undecided, with an uneasy feel; suggests an awkward, in-between state.
• RelatedおぼろげWrittenWritten/formal prose. For hazy memories and outlines, leaning on visual impressions. Not used for undecided outcomes.
• RelatedおぼつかないWrittenWritten/formal prose. For an unpromising or unreliable outlook, carrying a note of worry; centers on unease about the future.
• Related不明瞭ふめいりょうWrittenWritten/formal prose. For unclear wording or pronunciation, leaning toward unclear explanations; not about undecided outcomes.
• Antonym確定かくていNeutralAntonym. For something settled or fixed, the opposite of 「不確定」, as in 「日程が確定する」.
• Antonym確実かくじつNeutralAntonym. For something certain and reliable, sure to be correct; opposed to 「不確定」 on whether it is settled.

For an undecided schedule or plan, say 「未定」. In written, legal, or scientific contexts, use 「不確定」 for something not yet finalized, as in 「不確定要素」「不確定性原理」. For something unreliable, say 「不確か」. For the settled opposite, use 「確定」. The rest cover specific shades — 「不明」 for unknown causes, 「曖昧」 for vague wording, 「未解決」 for pending problems, 「あやふや」 for fuzzy recollections — so pick by what exactly is unclear.

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

1. はっきり確定かくていしないこと。定さだまらないこと。また、そのようなさま。