寰 is a literary/classical character almost never used alone in modern Chinese. Look for it in compounds:
寰宇 ("the universe"),
寰球 ("the globe"),
人寰 ("the world of the living", as in
惨绝人寰, "unprecedented in human history"), and
尘寰 ("the dusty world," Buddhist for "this mortal life"). Originally meant the royal domain within 1000 li of the imperial capital.
