ちゅうこく忠告chuukoku
1.

A heartfelt suggestion intended to correct someone's mistakes or shortcomings, often given with the intention of helping them avoid potential dangers or unfavorable outcomes.

2.

A personal recommendation delivered with genuine concern for someone's well-being, encouraging them to change their behavior or decisions for the better.

3.

A verbal admonition that serves to guide someone away from possible errors or harmful actions, emphasizing the importance of listening to the advice of trusted individuals.

Example:

私は彼に煙草を吸うなと忠告した。