There is often ambiguity between the terms "tower" and "mast". A tower is a self-supporting or cantilevered structure, while a mast is held up by stays or guys. Both towers and masts have limited floor space and are non-building structures, as opposed to regular buildings which have greater floor space for occupancy. The terminology is further confused through misuse. Skyscrapers are often referred to as "towers" and some towers use the term "mast". Ironically, "skyscraper" has some etymology from references to high sailboat masts.