How to say "unsure" in Japanese

• 心もとないこころもとない
  i-adjectiveCovers an 'unsure' feeling of unease or anxiety, as when you cannot rely on something and feel unsettled. It is a less common word, so learners will meet it mainly in reading rather than everyday speech.
• 怪しいあやしいJLPT N2approx.Common
  i-adjectiveCovers the 'unsure' sense of doubting or being uncertain about something, and also extends to 'doubtful' and 'unlikely'. It is a common word and usually the natural choice for expressing uncertainty.
  彼かれが時間じかんどおりに来くるかどうかは私は怪あやしいと思おもう。↗

  I question whether he'll come in time.

For 'unsure' meaning uncertain or doubtful about something, 「怪しい」 is the everyday choice; 「心もとない」 covers an uneasy, anxious sense of unsureness and is less common overall.

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

• 心もとないこころもとないuneasy
• 怪しいあやしいdoubtful