The digit or finger is an ancient and obsolete non- SI

unit of measurement A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other quantity of that kind can be expressed as a mult ...

of length. It was originally based on the breadth of a human finger. It was a fundamental unit of length in the Ancient Egyptian, Mesopotamian,

Hebrew Hebrew (; ; ) is a Northwest Semitic language of the Afroasiatic language family. Historically, it is one of the spoken languages of the Israelites and their longest-surviving descendants, the Jews and Samaritans. It was largely preserved ...

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...

and Roman systems of measurement. In astronomy a digit is one twelfth of the diameter of the sun or the moon.

History

Ancient Egypt

The digit, also called a finger or fingerbreadth, is a unit of measurement originally based on the breadth of a human finger. In Ancient Egypt it was the basic unit of subdivision of the

cubit The cubit is an ancient unit of length based on the distance from the elbow to the tip of the middle finger. It was primarily associated with the Sumerians, Egyptians, and Israelites. The term ''cubit'' is found in the Bible regarding ...

. On surviving Ancient Egyptian cubit-rods, the royal cubit is divided into seven palms of four digits or fingers each. The royal cubit measured approximately 525 mm, so the length of the ancient Egyptian digit was about 19 mm.

Mesopotamia

In the classical

Akkadian Empire The Akkadian Empire () was the first ancient empire of Mesopotamia after the long-lived civilization of Sumer. It was centered in the city of Akkad () and its surrounding region. The empire united Akkadian and Sumerian speakers under one rul ...

system instituted in about 2250 BC during the reign of

Naram-Sin Naram-Suen (Naram-Sin) may refer to any of four kings in the history of Mesopotamia: * Naram-Sin of Akkad (), an Akkadian king, the most famous of the four * Naram-Sin of Assyria (), an Assyrian king * Naram-Sin of Uruk (), a king of Uruk * Na ...

, the finger was one-thirtieth of a cubit length. The cubit was equivalent to approximately 497 mm, so the finger was equal to about 17 mm. Basic length was used in architecture and field division.

Ancient Hebrew system

Ancient Greece

Ancient Rome

Britain

A digit ( lat. ''digitus'', "finger"), when used as a unit of length, is usually a sixteenth of a foot or 3/4" ( 1.905 cm for the international

inch Measuring tape with inches The inch (symbol: in or ″) is a unit of length in the British imperial and the United States customary systems of measurement. It is equal to yard or of a foot. Derived from the Roman uncia ("twelft ...

). 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 A finger is a limb of the body and a type of digit, an organ of manipulation and sensation found in the hands of most of the Tetrapods, so also with humans and other primates. Most land vertebrates have five fingers (Pentadactyly). Chambers 1 ...

(7/6 digit), palm (4 digits), hand (16/3 digits), shaftment (8 digits),

span Span may refer to: Science, technology and engineering * Span (unit), the width of a human hand * Span (engineering), a section between two intermediate supports * Wingspan, the distance between the wingtips of a bird or aircraft * Sorbitan es ...

(12 digits),

(24 digits) and

ell An ell (from Proto-Germanic *''alinō'', cognate with Latin ''ulna'') is a northwestern European unit of measurement, originally understood as a cubit (the combined length of the forearm and extended hand). The word literally means "arm", and ...

(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.

Astronomy

In astronomy a digit is, or was until recently, one twelfth of the diameter of the sun or the moon. This is found in the

Moralia The ''Moralia'' ( grc, Ἠθικά ''Ethika''; loosely translated as "Morals" or "Matters relating to customs and mores") is a group of manuscripts dating from the 10th–13th centuries, traditionally ascribed to the 1st-century Greek scholar Plu ...

Plutarch Plutarch (; grc-gre, Πλούταρχος, ''Ploútarchos''; ; – after AD 119) was a Greek Middle Platonist philosopher, historian, biographer, essayist, and priest at the Temple of Apollo in Delphi. He is known primarily for his ...

, XII:23, but the definition as exactly one twelfth of the diameter may be due to

Ptolemy Claudius Ptolemy (; grc-gre, Πτολεμαῖος, ; la, Claudius Ptolemaeus; AD) was a mathematician, astronomer, astrologer, geographer, and music theorist, who wrote about a dozen scientific treatises, three of which were of import ...

. Sosigenes of Alexandria had observed in the 1st century AD that on a

dioptra A dioptra (sometimes also named dioptre or diopter, from el, διόπτρα) is a classical astronomical and surveying instrument, dating from the 3rd century BC. The dioptra was a sighting tube or, alternatively, a rod with a sight at b ...

, a disc with a diameter of 11 or 12 digits (of length) was needed to cover the moon. The unit was used in Arab or Islamic astronomical works such as those of Ṣadr al‐Sharīʿa al‐Thānī (d.1346/7), where it is called ar, إصبعا ''iṣba' '', digit or finger. The astronomical digit was in use in Britain for centuries. Heath, writing in 1760, explains that 12 digits are equal to the diameter in eclipse of the sun, but that 23 may be needed for the Earth's shadow as it eclipses the moon, those over 12 representing the extent to which the Earth's shadow is larger than the Moon. The unit is apparently not in current use, but is found in recent dictionaries.

Alcoholic Beverages

A 'finger' of an alcoholic beverage is colloquially referred to as a 'digit'.

References

{{DEFAULTSORT:Digit (Length) Units of length Human-based units of measurement