A light fixture (US English), light fitting (UK English), or luminaire is an electrical device used to create artificial light by use of an electric lamp. All light fixtures have a fixture body and a light socket to hold the lamp and allow for its replacement. Fixtures may also have a switch to control the light. Fixtures require an electrical connection to a power source; permanent lighting may be directly wired, and moveable lamps have a plug. Light fixtures may also have other features, such as reflectors for directing the light, an aperture (with or without a lens), an outer shell or housing for lamp alignment and protection, and an electrical ballast or power supply. A wide variety of special light fixtures are created for use in the automotive lighting industry, aerospace, marine and medicine.