The ligne (pronounced [liɲ] ) or line or Paris line, is a historic unit of length used in France and elsewhere prior to the adoption of the metric system in the late 18th century, and used in various sciences after that time. The loi du 19 frimaire an VIII (Law of 10 December 1799) states that one metre is equal to exactly 443.296 French lines.
|1 ligne in ...||... is equal to ...|
|French units|| 12 Truchet point|
|metric (SI) units||2.2558 mm|
|imperial/US units||0.08881 in|
There are 12 lignes to one French inch (pouce). The standardized conversion for a ligne is 2.2558291 mm (1 mm = 0.443296 ligne), and it is abbreviated with the letter L or represented by the triple prime, ‴. One ligne is the equivalent of 0.0888 international inch.
In the 18th century German button makers began to use the term ligne to measure the diameter of buttons. The consensus definition was that a ligne was the measurement of a round wick, folded flat. In this sense it measures 1⁄40 of an inch, but not exactly, for there were several inches in the kingdoms and petty states of Germany at that time.
Such a measurement became the American measurement called "line", being one-fortieth of the US-customary inch, used measure buttons, probably introduced by German immigrants. It remains in US use today for buttons and snaps.
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Chaque ligne équivaut à 2,2558 mm, arrondis à 2,26 mm pour calculer plus rapidement. [Each line equals 2.2558 mm, rounded to 2.26 mm for faster calculation.]. (in French)
- Oxford English Dictionary