An extension cord, power extender, or extension lead is a length of flexible electrical power cable (flex) with a plug on one end and one or more sockets on the other end (usually of the same type as the plug). The term usually refers to mains (household AC) extensions but is also used to refer to extensions for other types of cabling. If the plug and receptacle are of different types, the term "adapter cord" may be used.
Extension cords come in various lengths and thicknesses, and service duties. In general, the more power needed by the appliance, the thicker the cord should be (that is, larger wires inside). Cords to be used outdoors, in wet areas, around oils, or exposed to sunlight for long periods should be selected for such specific service. An extension reel is an extension lead that rolls up, usually into the socket end, which in some cases has more than one socket on it (often 2 or 4). Another type of extension reel hangs near the plug end and permits the user to draw the cord out by grasping the socket end.