What is a condominium unit or apartment?

I was recently talking to a friend of mine that is purchasing a unit in a highrise condominium project that hasn't been built yet. He made the remark that he's only buying air 80 feet in the sky. I said that wouldn't change very much once the building was built.

Under Hawaii condo law a condominium property regime consists of common elements (including limited common elements) and apartments. The condominium declaration defines what part of the project is an apartment, common element or limited common elements. Almost every condominium declaration in Hawaii first defines the apartment and states that everything else is a part of the common elements. Certain designated portions of the common elements are limited common elements.

Most condominium associations use an airspace definition for the apartments. The reason it is called an airspace definition is that the apartment is essentially a bubble made up of air, paint, carpeting and interior non-load-bearing walls. The boundaries of most apartments are the interior decorated surfaces of the perimeter of the apartment. Everything inside the decorated surfaces other than load-bearing walls and utilities that serve more than one apartment are part of the apartment.

The part of the condominium project that my friend is going to own by himself is the apartment, while he'll jointly own the structural elements of the project with the other members, he will mostly own air even after the condominium project is built.