alert

Condition of heightened watchfulness or preparation for action.

“bombers were put on alert during the crisis”

A warning serves to make you more alert to danger.

An automatic signal (usually a sound) warning of danger.

Warn or arouse to a sense of danger or call to a state of preparedness.

“We alerted the new neighbors to the high rate of burglaries”

Engaged in or accustomed to close observation.

“caught by a couple of alert cops”

“alert enough to spot the opportunity when it came”

Mentally perceptive and responsive.

“an alert mind”

“alert to the problems”

Quick and energetic.