[1] The width of the palm was a traditional unit in Ancient Egypt, Israel, Greece, and Rome and in medieval England, where it was also known as the hand,[2][a] handbreadth,[3] or handsbreadth.
[c] The unit is attested as early as the reign of Djer, third pharaoh of the First Dynasty,[5] and appears on many surviving cubit-rods.
Six made up the "Greek cubit" (meh nedjes) of about 45 cm (1 ft 6 in).
[13] These various palms were divided into four digits (dáktylos) or two "middle phalanges" (kóndylos).
[15] The Roman palm (Latin: palmus) or lesser palm (palmus minor) made up ¼ of the Roman foot (pes), which varied in practice between 29.2–29.7 cm (11.5–11.7 in)[16] but is thought to have been officially 29.6 cm (11.7 in).
[19] The palms of medieval (Latin: palma)[20] and early modern Europe—the Italian, Spanish, and Portuguese palmo and French palme—were based upon the Roman "greater palm", reckoned as a hand's span or length.
The English palm, handbreadth, or handsbreadth is three inches[30][31][32][33] (7.62 cm)[g] or, equivalently, four digits.
[31][h] The palm was excluded from the British Weights and Measures Act 1824 that established the imperial system and is not a standard US customary unit.