An electrical extension cord, extension cord, electric extension cord, electric extension cord, extension cord or extension cord is a segment of flexible electrical cord, with a plug at one end and one or more outlets at the other (usually the same type as the plug). The term is usually used for electrical cable extensions for domestic use, but it is also valid to refer to other types of cable extensions (network, telephone, USB cable...). If the plug or connector at one end is of a different type than the other end, rather than extension it should be called adapter cable.

A power strip is a block with several outlets (usually 3 or more, placed in a line). The multiple can be inserted into one of the ends of the extension cord, with the entire assembly usually being called extension cord, electrical extension cord or multiple extension cord.

In the coiled type, to avoid overheating of the cable if it is used for high powers (especially with inductive loads), it is recommended to unroll it completely.