noun
teachings left by a deceased person; last instructions
Refers to moral or practical teachings passed down by someone who has died, often a respected figure like a parent, teacher, or historical person. Carries a formal, somewhat solemn tone.
祖父の遺訓を守って、正直に生きている。
I live honestly, following my grandfather's last teachings.
彼は父の遺訓を胸に刻んで政治家になった。
He became a politician with his father's dying instructions engraved in his heart.
Compound of 遺 (い, 'leave behind') and 訓 (くん, 'teaching, instruction'). The kanji combination directly conveys the meaning of teachings left behind after death.