Definition of Microinch

An inch is an Imperial unit of length. Sweden also briefly had a "decimal inch" based on the metric system.

According to some sources, the inch was originally defined informally as the distance between the tip of the thumb and the first joint of the thumb. Another source says that the inch was at one time defined in terms of the yard, supposedly defined as the distance between Henry I of England's nose and his thumb. There are twelve inches in a foot, and three feet in a yard.

The word for "inch" is similar to the word for "thumb" in some languages. French: pouce inch, pouce thumb; Italian: pollice inch, pollice thumb; Spanish: pulgada inch, pulgar thumb; Swedish: tum inch, tumme thumb. In Dutch it is even the same: duim inch and thumb.