teacher (to whom one owes a debt of gratitude); mentor; one's former teacher
恩師の言葉が今も胸に刻まれている。
My mentor's words are still engraved in my heart.
卒業後も恩師を訪ねて近況を報告した。
Even after graduation, I visited my mentor to report how I was doing.
恩師に導かれて研究者の道を歩んだ。
Guided by my mentor, I walked the path of a researcher.