Warn

verb (used with object)
1.
to give notice, advice, or intimation to (a person, group, etc.) of danger, impending evil, possible harm, or anything else unfavorable:
They warned him of a plot against him. She was warned that her life was in danger.
2.
to urge or advise to be careful; caution:
to warn a careless driver.
3.
to admonish or exhort, as to action or conduct:
She warned her employees to be on time.
4.
to notify, advise, or inform:
to warn a person of an intended visit.
5.
to give notice to (a person, group, etc.) to go, keep at a distance, etc. (often followed by away, off, etc.):
A sign warns trespassers off the grounds. A marker warned boats away from the dock.
6.
to give authoritative or formal notice to (someone); order; summon:
to warn a person to appear in court.
verb (used without object)
7.
to give a warning; caution:
to warn of further disasters.
verb
1.
to notify or make (someone) aware of danger, harm, etc
2.
(transitive; often takes a negative and an infinitive) to advise or admonish (someone) as to action, conduct, etc: I warn you not to do that again
3.
(takes a clause as object or an infinitive) to inform (someone) in advance: he warned them that he would arrive late
4.
(transitive; usually foll by away, off, etc) to give notice to go away, be off, etc: he warned the trespassers off his ground