SPAN (from O. Eng. spannan, to bind, connect together; the word is of general occurrence in Teutonic languages, the ultimate origin being the root spa-, to extend, stretch out, cf. Gr. (rirav, to draw out, Lat. spatium, space), a distance stretched, the space between terminal points. The word was formerly used as a measure of length= 10-368 in., taken from the stretch of the fully opened hand from thumb to little finger. The term is used in architecture for the width or opening of an arch or arched opening, and also the width of a roof between the wall plates. A " span roof " is a roof having two sides inclining to a centre or ridge, in contradistinction to a " shed roof " (see SHED).
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)