How to say "ascertain" in Japanese

• ただすCommon
  godan verb, transitive verbFor ascertaining or verifying something — establishing the truth of a matter, as when you check the facts behind what you have been told. Usually written in kana rather than with kanji.
  校長こうちょうは彼かれに無断欠勤むだんけっきんの理由りゆうをただした。↗

  The principal called him to account for being absent without an excuse.
• 確かめるたしかめるJLPT N3approx.Common
  ichidan verb, transitive verbThe general-purpose choice for making sure of something or checking it: use this when you simply want to confirm a fact or detail and no special nuance is needed.
  窓まどが閉しまっているか確たしかめとけ。↗

  See that the window is closed.
• 突き止めるつきとめるCommon
  ichidan verb, transitive verbAscertaining something by getting to the bottom of it: determining the underlying cause of a problem, identifying a culprit, or pinning down exactly where something is.
  ホームページに住所じゅうしょを書かいたら、その気きになれば誰だれでもあなたの居所いどころを突き止つきとめられる。↗

  If you write your address on a web-page, anybody can find out where you live if the whim takes them.
• 見届けるみとどけるCommon
  ichidan verb, transitive verbAscertaining something by seeing it with your own eyes: watching an event or undertaking through to the end to make sure of how it turns out.
• 見定めるみさだめるCommon
  ichidan verb, transitive verbAscertaining by observation: looking carefully at something to judge what it is, so that you grasp the situation clearly.

Use 「確かめる」 for general making sure or checking, 「ただす」 for verifying the truth of a matter, 「突き止める」 for pinning down a culprit or cause, 「見届ける」 for watching something through to the end, and 「見定める」 for judging by looking.

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

• ただすto ascertain
• 確かめるたしかめるto make sure
• 突き止めるつきとめるto determine (esp. a culprit or underlying cause)
• 見届けるみとどけるto make sure of
• 見定めるみさだめるto make sure of
• 聞きただすききただすto find out the truth
• 見極めるみきわめるto ascertain