How to say "undecided" in Japanese

• 未定みていJLPT N1approx.Common
  no-adjective, na-adjectiveThe everyday word for something not yet fixed — a plan, date, or arrangement that is still open. It covers the neutral 'TBD' sense of 'undecided' and is usually the safest choice.
  計画けいかくはまだ未定みていである。↗

  The plans are still up in the air.
• 未決みけつCommon
  no-adjectiveUse it when the point is that a decision or settlement is still outstanding, as with pending or unresolved matters; for plans and dates that are simply not yet fixed, 未定 is the usual word.
  訴訟そしょうは未決みけつである。↗

  The lawsuit remains undecided.
• うやむやCommon
  na-adjective, nounRarely the word for neutral 'undecided': it really means vague, hazy, or left unclear, often suggesting that something is being glossed over or evaded rather than simply not yet decided.
  その問題もんだいをうやむやにしておくことはできない。↗

  We shouldn't leave the matter unsettled.

For 'undecided' about plans or details not yet fixed, use 未定; for matters still pending a decision, 未決; 「うやむや」 is not a neutral 'undecided' — it means vague or left unclear, often evasively.

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

• 未定みていnot yet fixed
• 未決みけつpending
• うやむやindefinite
• 未決定みけっていundecided
• 不決定ふけっていpending
• 未確定みかくていunconfirmed