observant (adj.)

• active
• advertent
• agog
• alert
• assiduous
• attentive
• awake
• aware
• careful
• compliant
• concentrated
• conforming
• conscientious
• conscious
• constant
• custodial
• deferential
• devoted
• devout
• diligent
• duteous
• dutiful
• eagle-eyed
• earnest
• ethical
• faithful
• finical
• finicky
• guarded
• hawk-eyed
• heedful
• intense
• intent
• keen
• keen-eyed
• lidless
• loyal
• meticulous
• mindful
• moral
• nice
• niggling
• obedient
• observing
• open-eyed
• openmouthed
• perceptive
• prudent
• punctilious
• punctual
• regardful
• respectful
• scrupulous
• sharp
• sharp-eyed
• shrewd
• sleepless
• thoughtful
• true
• vigilant
• wary
• watchful