Palm (unit)

The palm is an archaic unit of length, traditionally based on the width of a human hand. Its exact length varies depending on the historical period and geographical location.

Typically, a palm is considered to be equivalent to four digits (finger widths). However, variations exist, with some definitions equating a palm to three inches or even to the length of the hand from the wrist to the base of the fingers.

The palm was used in ancient Egypt, Mesopotamia, Greece, and Rome, among other civilizations. Different "palms" existed within these regions, each with a slightly different standard. For example, the Roman palm (palmus major) was approximately 7.4 centimeters, while the ancient Egyptian palm was about 7.5 centimeters.

The unit is now largely obsolete in modern metrology, having been superseded by standardized units such as the meter and the foot. However, the term "palm" may still be used informally or in historical contexts. Its ambiguity makes it unsuitable for precise measurements.