Definition of warns:
(v) :
(transitive) To make (someone) aware of impending danger, evil, etc.
(v) :
(transitive) To make (someone) aware of (something impending); especially:
(v) :
(transitive) To caution or admonish (someone) against unwise or unacceptable behaviour.
(v) :
(transitive) To notify or inform (someone, about something).
(v) :
(chiefly with "off", "away", and similar words) To advise or order to go or stay away.
(v) :
(intransitive) To give warning.