To sense, suspect, or get an inkling of something; to become aware of a hint or change (often used when someone suspects a plot or deception).
彼は部長が何かを隠していると、早くから感づいていた。
He had sensed early on that the manager was hiding something.
妻は夫の様子から浮気に感づいたようだ。
It seems the wife sensed her husband's affair from his behavior.
会議の雰囲気から、社員たちは問題の深刻さに感づき始めた。
From the meeting's atmosphere, the employees began to sense the seriousness of the problem.
足音が近づくのを聞いて、彼女は誰かが来たことに感づいた。
Hearing footsteps approach, she sensed that someone had come.