warn

Advise or counsel in terms of someone's behavior.

“I warned him not to go too far”

“I warn you against false assumptions”

Ask to go away.

“The old man warned the children off his property”

Notify of danger, potential harm, or risk.

“The director warned him that he might be fired”

“The doctor warned me about the dangers of smoking”

Notify, usually in advance.

“I warned you that I would ask some difficult questions”