A house is a structure built for a single family to live in. It is usually detached from other structures, but houses can also adjoin other buildings. Houses can be subdivided into multiple units, but structures built or designed for multiple units are not classified as houses. Houses include mansions, but palaces are classified separately. Houses can be adapted for many non-residential uses, but their form is governed by the needs of residential use.

The single-family origin distinguishes the form from a building designed for multiple units. A house can be attached to another building without losing that original design basis.

Later subdivision or nonresidential use can occur in a house. The residential arrangement that governed its form remains distinct from its current occupancy.