To extend a length or period; to lengthen

An extension of length or period; lengthening / An extension of a rail line, road, etc.

(geometry, engineering) extended line (usually as an auxiliary line) / extension of a traffic route (e.g. highway or railway line) / (figuratively) extension or result developed from an existing thing

An extra game of soccer, baseball, martial arts, etc; an extra time; an extra innings.

An extension cord.