Use of an artificial source of light for illumination.
It is a key element of architecture and interior design. Residential lighting uses mainly either incandescent lamps or fluorescent lamps and often depends heavily on movable fixtures plugged into outlets; built-in lighting is typically found in kitchens, bathrooms, and corridors and in the form of hanging pendants in dining rooms and sometimes recessed fixtures in living rooms. Lighting in nonresidential buildings is predominantly fluorescent. High-pressure sodium-vapor lamps (see electric discharge lamp ) have higher efficiency and are used in industrial applications. Halogen lamps have residential, industrial, and photographic applications. Depending on their fixtures, lamps (bulbs) produce a variety of lighting conditions. Incandescent lamps placed in translucent glass globes create diffuse effects; in recessed ceiling-mounted fixtures with reflectors, they can light walls or floors evenly. Fluorescent fixtures are typically recessed and rectangular, with prismatic lenses, but other types including indirect cove lights (see coving ) and luminous ceilings, in which lamps are placed above suspended translucent panels. Mercury-vapor and high-pressure sodium-vapor lamps are placed in simple reflectors in industrial spaces, in pole-mounted streetlight fixtures, and in indirect up-lighting fixtures for commercial applications.