alert - noun

condition of heightened watchfulness or preparation for action

a warning serves to make you more alert to danger

an automatic signal (usually a sound) warning of danger

alert - verb

• warn or arouse to a sense of danger or call to a state of preparedness

alert - adjective

• engaged in or accustomed to close observation
• quick and energetic
• mentally perceptive and responsive

alert - thesaurus

alarm   alarum   alerting   alive   awake   brisk   lively   merry   rattling   snappy   watchful   zippy