alertness

(noun) the process of paying close and continuous attention. Synonyms: watchfulness, wakefulness, vigilance. Examples: "Wakefulness, watchfulness, and bellicosity make a good hunter." "Vigilance is especially susceptible to fatigue."

(noun) a state of readiness to respond. Synonyms: alerting. Example: "Alerting was indicated by the desynchronization of the eeg."

(noun) lively attentiveness. Synonyms: sharp-sightedness, on the qui vive.