/ əbˈzɜːvənt; NAmE -ˈzɜːrv-/ adjective
1.
good at noticing things around you
SYN sharp-eyed :
Observant walkers may see red deer along this stretch of the road.
How very observant of you!
2.
( formal ) careful to obey religious laws and customs
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WORD ORIGIN
late Middle English (as a noun): from French , literally watching , present participle of observer , from Latin observare to watch, from ob- towards + servare attend to, look at.