|≈||approximately equal to|
|digits||indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369 …)|
A chain is a unit of length. It measures 66 feet, or 22 yards, or 100 links, or 4 rods (20.1168 m). There are 10 chains in a furlong, and 80 chains in one statute mile. An acre is the area of 10 square chains (that is, an area of one chain by one furlong). The chain has been used for several centuries in Britain and in some other countries influenced by British practice.
The line (abbreviated L or l) was a small English unit of length, variously reckoned as 1⁄10, 1⁄12, 1⁄16, or 1⁄40 of an inch. It was not included among the units authorized as the British Imperial system in 1824.