On top & on top of

[nvlcsw]

I had a student ask me what the difference was and I choked
It seems as though the "of" is implied in On top. "Of all the groups, I'm on top." "The book is on top."
Not a grammar ninja
Life IS Good³
Christopher
Reno, NV

[David L.]

"See the pile of books over there? The book you want is on top."

"The suitcases are stored away. The big one is on top of the wardrobe."

= on top of (something)