The line is a unit of measurement, one line being equal to of an English (prior to 1824) inch. It was defined as one-quarter of a barleycorn, which defined the inch even before 1066. The French (prior to 1799) ligne was similarly defined as of the pouce (meaning "thumb", about an inch). Since the French pouce or inch was about 6% longer than the English inch, the "line" was similarly longer. The Russian liniya was defined as of the diuym (inch) from the 16th to the early 20th century; the diuym itself was redefined as exactly an English inch by Peter the Great. The German linie is described in the article German units of measurement as "usually inch, but also ". Since the Russian military and German manufacturing were major factors in arms procurement, the "-inch line" became common terminology concerning weapons.

In Typography Line length is the width occupied by a block of typeset text, measured in inches, picas and points. A block of text or paragraph has a maximum line length that fits a determined design.

Die Linie ist ein früheres Längenmaß für die Feinmechanik. Ihre Länge unterschied sich in den einzelnen Ländern geringfügig und entspricht meistens einem Zwölftel des jeweiligen Zoll.