observant

Having or showing keen perceptiveness; perceptive.

Diligent in observing a law, custom, duty, or principle.

Watching; watchful; observing; having or characterized by good powers of observation, or attention, care, accuracy, etc., in observing: as, an observant mind; a man of observant habits.

Attentive; obedient; submissive; ready to obey and serve; hence, obsequious: with to or of before a personal object.

Carefully attentive in observing or performing whatever is prescribed or required; strict in observing and practising: with of: as, he was very observant of the rules of his order; observant of forms.

Synonyms and

Watchful, mindful, heedful, regardful.

An observer.

An obsequious or slavish attendant.

One who is strict in observing or complying with a law, rule, custom, etc.