alert

very attentive or observant

• “an alert and responsive baby is a joy”
• “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”

mentally responsive

• “an alert mind”

not unconscious; especially having become conscious

• “the patient is now awake and alert”

(usually followed by `to'') showing acute awareness; mentally perceptive

• “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”

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”

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