Interior Architecture is truly a marriage of three distinct design disciplines: interior design, architecture, and industrial design. Interior design focuses on the selection of interior materials, finishes, and furnishings; architecture on the design of building forms and systems; and industrial design on the design of manufactured products.

Another definition is the specific features of a building's interior. It can also be the initial design and plan for use, the later redesign to accommodate a changed purpose, or a significantly revised design for adaptive reuse of the building shell.

The latter is often part of sustainable architecture practices, conserving resources through "recycling" a structure by adaptive redesign. Generally referred to as the spatial art of environmental design, form and practice, interior architecture is the process through which the interiors of buildings are designed, concerned with all aspects of the human uses of structural spaces.