To refrain from talking, especially to remain silent about something that may be sensitive or secret.
To notify or inform (someone, about something).
To caution or admonish (someone) against unwise or unacceptable behaviour.
To give warning.
To summon (someone) to or inform of a formal meeting or duty.
To advise or order to go or stay away.
To make (someone) aware of impending danger, evil, etc.