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; "The empty house alarmed him"; "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"; "constantly alert and vigilant, like a sentinel on duty"

quick and energetic; "a brisk walk in the park"; "a lively gait"; "a merry chase"; "traveling at a rattling rate"; "a snappy pace"; "a spanking breeze"

mentally perceptive and responsive;"an alert mind"; "alert to the problems"; "alive to what is going on"; "awake to the dangers of her situation"; "was now awake to the reality of his predicament"