palm

   1. a traditional unit of distance equal to the width of a person's palm. The palm equals 4 digits or 1/6 cubit, which is about 3 inches or 7.5 centimeters. This unit was used very commonly in medieval and early modern Britain. Similar units, all equal to 1/4 the local "foot" unit, were used throughout northern Europe.

   2. a traditional unit of distance equal to the length of a person's hand, from the wrist to the end of the middle finger. In the English system this unit is equal to 9 inches (22.86 centimeters) and is usually called a span. The confusion between the two palm units is ancient. In Roman times, the longer unit was known as the palmus major and the shorter one as the palmus minor. In the nineteenth century, the 3-inch version was more common in Britain and the 9-inch version was more common in the U.S., perhaps because some Americans were familiar with the comparable Spanish palmo (see below).

   3. a name sometimes used in Dutch for the decimeter (10 centimeters, or about 3.937 inches).