was a small English unit of length, variously reckoned as 1⁄10, 1⁄12, 1⁄16, or 1⁄40 of an inch.
[5] The US button trade uses the same or a similar term but defined as one-fortieth of the US-customary inch (making a button-maker's line equal to 0.635 mm (0.0250 in)).
[6][7] Botanists formerly used the units (usually as 1⁄12 inch) to measure the size of plant parts.
[8] Entomologists in the UK and other European countries in the 1800s used lines as a unit of measurement for insects, at least for the relatively large mantids and phasmids.
Examples include Westwood,[9][10] in the UK, and de Haan[11] in the Netherlands.