an opening or hollow that forms a holder for something

an electromagnetic device for remote or automatic control that is actuated by variation in conditions of an electric circuit and that operates in turn other devices (such as switches) in the same or a different circuit

a complete lighting unit

a backup pathway that provides an alternating route for the current to flow back to the ground if there is a fault in the wiring system

something that is installed for use

an electric lamp in which the discharge takes place through mercury vapor

white, glowing, or luminous with intense heat