observant
adj.good at noticing small details or changes that other people might miss. It can also describe someone who follows all the rules of their religion.
adj.quick to notice or perceive things; alert and attentive to detail. Also describes strict adherence to the laws and rituals of a particular religion or custom.
“She is very observant and noticed my new haircut immediately.”
“An observant passerby noticed the smoke coming from the basement window and called the fire department before the alarm even sounded.”
“The detective remained silent and observant throughout the interview, noting the slight tremor in the suspect's hands whenever the victim's name was mentioned.”
Often used predicatively after linking verbs like 'remain' or 'stay'.
“Observant Muslims pray five times daily, so students and employees sometimes need a space to pray – an accommodation that can be as simple as being excused briefly from class or work.”