Atop means on top of something or at the highest point. A flag flies atop a flagpole. A weather vane sits atop a barn roof. When you finally reach the summit after a long hike, you're standing atop the mountain.

The word suggests being positioned at the very highest point of something, usually something tall or elevated. You might place a star atop a Christmas tree, or notice a bird's nest atop a telephone pole. In fantasy stories, a dragon might guard treasure atop a remote peak.

Atop works differently than “on top of” because it sounds more formal and often emphasizes height or achievement. You could say “the castle sits on top of the hill” or “the castle sits atop the hill.” The second version makes the castle sound more impressive and commanding. When a news article describes someone as being atop the rankings or atop their field, it means they've reached the highest level of success.