Most apartments are in buildings designed for the purpose, but large older houses are sometimes divided into apartments. The word apartment connotes a residential unit or section in a building. Apartment building owners, lessors, or managers often use the more general word units to refer to apartments. Units can be used to refer to rental business suites as well as residential apartments. When there is no tenant occupying an apartment, the lessor is said to have a vacancy. Lessors objectives are often to minimize the vacancy rate for their units. Apartment types and characteristics Luxury apartment buildings in Gurgaon, Delhi metropolitan areaApartments can be classified into several types. Studio or efficiency or bachelor apartments tend to be the smallest apartments with the cheapest rents in a given area. These kinds of apartment usually consist mainly of a large room which is the living, dining, and bedroom combined. There are usually kitchen facilities as part of this central room, but the bathroom is its own smaller separate room. Permanent carpeting is often included in an apartment. Sefid apartments in Tehran, IranLaundry facilities are usually kept in a separate area accessible to all the tenants in the building.

Outlets for connection to telephones are typically included in apartments. Telephone service is optional and is practically always billed separately from the rent payments. Cable television and similar amenities are extra also. Rental leases often limit the maximum number of people who can reside in each apartment. Every unit typically gets its own mailbox with individual keys to it. In larger buildings, garbage is often collected in a common trash bin or dumpster. For cleanliness or minimizing noise, many lessors will place restrictions on tenants regarding keeping pets in an apartment. An industrial, warehouse, or commercial space converted to an apartment is commonly called a loft. Staying in privately owned apartments rather than in a hotel is quickly becoming popular with travellers.