What is Apartment?

Legal Definition
An apartment (in American and Canadian English) or a flat (in British English) is a self-contained housing unit (a type of residential real estate) that occupies only part of a building, correctly, on a single level without a stair. Such a building may be called an apartment building, apartment complex, flat complex, block of flats, tower block, high-rise or, occasionally mansion block (in British English), especially if it consists of many apartments for rent. In Scotland it is called a block of flats or, if it's a traditional sandstone building, a tenement, which has a pejorative connotation elsewhere. Apartments may be owned by an owner/occupier, by leasehold tenure or rented by tenants (two types of housing tenure).
-- Wikipedia
Legal Definition
A part of a house occupied by a person, while the rest is occupied by another, or others. 7 Mann. & Gr. 95 ; 6 Mod. 214 ; Woodf. L. & T. 178. See House.
-- Bouviers Law Dictionary
Legal Definition
A part of a house occupied by a person, while the rest ls occupied by another or others. As to the meaning of this term, see 7 Man. & G. 95; 6 Mod. 214; McMillan v. Solomon, 42 Ala. 356, 94 Am. Dec. 654; Commonwealth v. Estabrook, 10 Pick. (Mass.) 293; McLellan v. Dalton, 10 Mass. 190; People v. St Clair, 38 CaL 137.
-- Black's Law Dictionary
Legal Definition
A part of a house occupied by one person while the rest is occupied by another or others. See 10 Pick. (Mass.) 293.
-- Ballentine's Law Dictionary