Digit (unit)
unit of length
A digit (Latin: digitus, "finger") can be used as a unit of length. When used as a unit of length, is usually a sixteenth of a foot or 3/4" (1.905 cm for the international inch). The width of an adult human male finger tip is indeed about 2 centimetres. In English this unit has mostly fallen out of use, as do others based on the human arm: finger (7/6 digit), palm (4 digits), hand (16/3 digits), shaftment (8 digits), span (12 digits), cubit (24 digits) and ell (60 digits).
It is in general equal to the foot-nail, although the term nail can also be used as 1/16 of yard and other units.