A condominium, or condo, is the form of housing tenure
Housing tenure
Housing tenure refers to the financial arrangements under which someone has the right to live in a house or apartment. The most frequent forms are tenancy, in which rent is paid to a landlord, and owner occupancy. Mixed forms of tenure are also possible....

 and other real property
Real property
In English Common Law, real property, real estate, realty, or immovable property is any subset of land that has been legally defined and the improvements to it made by human efforts: any buildings, machinery, wells, dams, ponds, mines, canals, roads, various property rights, and so forth...

 where a specified part of a piece of real estate (usually of an apartment
An apartment or flat is a self-contained housing unit that occupies only part of a building...

 house) is individually owned while use of and access to common facilities in the piece such as hallways, heating system, elevators, exterior areas is executed under legal rights associated with the individual ownership and controlled by the association of owners that jointly represent ownership of the whole piece.

Colloquially, the term is often used to refer to the unit itself in place of the word "apartment".