v .
to determine with certainty ; to find out definitely 확실하게 정하다 ; 명확하게 알아내다

• With a quick flick of his tongue, Herbert ascertained that the pie that had just landed on his face was indeed lemon meringue.
• The police tried to trace the phone call, but they were unable to ascertain the exact location of the caller.
• Lary believed his wife was seeing another man ; the private detective ascertained that that was the case.