A building or edifice is an enclosed structure with a roof, walls and often windows, usually standing permanently in one place, such as a house or factory. Buildings come in a variety of sizes, shapes, and functions, and have been adapted throughout history for numerous factors, from building materials available, to weather conditions, land prices, ground conditions, specific uses, prestige, and aesthetic reasons. To better understand the concept, see Nonbuilding structure for contrast.

Buildings serve several societal needs – occupancy, primarily as shelter from weather, security, living space, privacy, to store belongings, and to comfortably live and work. A building as a shelter represents a physical separation of the human habitat (a place of comfort and safety) from the outside (a place that may be harsh and harmful at times).

Buildings have been objects or canvasses of much artistic expression. In recent years, interest in sustainable planning and building practices has become an intentional part of the design process of many new buildings and other structures, usually green buildings.

A building is 'a structure that has a roof and walls and stands more or less permanently in one place'; "there was a three-storey building on the corner"; "it was an imposing edifice". In the broadest interpretation a fence or wall is a building. However, the word structure is used more broadly than building, to include natural and human-made formations and ones that do not have walls; structure is more often used for a fence. Sturgis' Dictionary included that "[building] differs from architecture in excluding all idea of artistic treatment; and it differs from construction in the idea of excluding scientific or highly skillful treatment."

Structural height in technical usage is the height to the highest architectural detail on the building from street level. Spires and masts may or may not be included in this height, depending on how they are classified. Spires and masts used as antennas are not generally included. The distinction between a low-rise and high-rise building is a matter of debate, but generally three stories or less is considered low-rise.

There is clear evidence of homebuilding from around 18,000 BC. Buildings became common during the Neolithic period.

Single-family residential buildings are most often called houses or homes. Multi-family residential buildings containing more than one dwelling unit are called duplexes or apartment buildings. Condominiums are apartments that occupants own rather than rent. Houses may be built in pairs (semi-detached) or in terraces, where all but two of the houses have others on either side. Apartments may be built around courtyards or as rectangular blocks surrounded by plots of ground. Houses built as single dwellings may later be divided into apartments or bedsitters, or converted to other uses (e.g., offices or shops). Hotels, especially of the extended-stay variety (apartels), can be classed as residential.

Building types may range from huts to multimillion-dollar high-rise apartment blocks able to house thousands of people. Increasing settlement density in buildings (and smaller distances between buildings) is usually a response to high ground prices resulting from the desire of many people to live close to their places of employment or similar attractors.