What`s the difference between "window-shop" and "window shop"?
Can i use it as a verb? like "i`m window-shopping" or "i`m going to window-shopping" or "i`ve already window-shopped"?

Question

What`s the difference between "window-shop" and "window shop"? 
Can i use it as a verb? like "i`m window-shopping" or "i`m going to window-shopping" or "i`ve already window-shopped"?

Answer

Window-shop is a verb tense. You can say I am window-shopping, I window-shopped yesterday. In window shop (without the hyphen) you're describing a type of shop...a shop that sells windows. (Window is being used as an adjective. telling what kind of shop.)