In electrical and mechanical trades and manufacturing, each half of a pair of mating connectors or fasteners is conventionally designated as male or female, a distinction referred to as its gender. The female connector is generally a receptacle that receives and holds the male connector. Alternative terms such as plug and socket or jack are sometimes used, particularly for electrical connectors.
The assignment is a direct analogy with male and female genitalia. The part bearing one or more protrusions, or which fits inside the other, is designated male, while the one with the corresponding indentations, or fitting outside the other, is designated female. Extension of the analogy results in the verb to mate being used to describe the process of connecting two corresponding parts together.