A particularly 'observant' child, he noticed even the slightest changes in the classroom.
an 'observant' Jew/Muslim = a Jew/Muslim who is 'observant' of Jewish/Islamic law
Good reporters are keenly 'observant' of everything around them.
(..) Come on. It'll take two minutes. You're probably late already. I don't see anything. You don't? You're gonna have to be more observant, Susie. What is it? - I washed my hands! - Give me five. Hey, hey, hey, you gotta dry them. All right. (..)2009 The Lovely Bones