Editing Duodecimal (section)

== Origin ==
:''In this section, numerals are in [[decimal]]. For example, "10" means 9+1, and "12" means 9+3.''

[[Georges Ifrah]] speculatively traced the origin of the duodecimal system to a system of [[finger counting]] based on the knuckle bones of the four larger fingers. Using the thumb as a pointer, it is possible to count to 12 by touching each finger bone, starting with the farthest bone on the fifth finger, and counting on. In this system, one hand counts repeatedly to 12, while the other displays the number of iterations, until five dozens, i.e. the 60, are full. This system is still in use in many regions of Asia.<ref>{{cite journal |last=Pittman |first=Richard |date=1990 |title=Origin of Mesopotamian duodecimal and sexagesimal counting systems |journal=Philippine Journal of Linguistics |volume=21 |issue=1 |page=97}}</ref><ref name="Ifrah 2000">{{Cite book| last = Ifrah| first = Georges| author-link = Georges Ifrah| title = The Universal History of Numbers: From prehistory to the invention of the computer| publisher = Wiley | year=2000 |orig-year=1st French ed. 1981 | isbn = 0-471-39340-1}} Translated from the French by David Bellos, E. F. Harding, Sophie Wood and Ian Monk.</ref>

Languages using duodecimal number systems are uncommon. Languages in the [[Nigeria]]n Middle Belt such as [[Janji language|Janji]], [[Gbiri-Niragu language|Gbiri-Niragu]] (Gure-Kahugu), [[Piti language|Piti]], and the Nimbia dialect of [[Gwandara language|Gwandara]];<ref>{{Cite web |last=Matsushita |first=Shuji |date=October 1998 |title=Decimal vs. Duodecimal: An interaction between two systems of numeration |url=http://www3.aa.tufs.ac.jp/~P_aflang/TEXTS/oct98/decimal.html |url-status=dead |archive-url=https://web.archive.org/web/20081005230737/http://www3.aa.tufs.ac.jp/~P_aflang/TEXTS/oct98/decimal.html |archive-date=October 5, 2008 |access-date=May 29, 2011 |website=www3.aa.tufs.ac.jp}}</ref> and the [[Chepang language]] of [[Nepal]]<ref>{{Cite book
| contribution=Les principes de construction du nombre dans les langues tibéto-birmanes
| first=Martine
| last=Mazaudon
| title=La Pluralité
| editor-first=Jacques
| editor-last=François
| date=2002
| pages=91–119
| publisher=Peeters
| place=Leuven
| isbn=90-429-1295-2
| url=http://lacito.vjf.cnrs.fr/documents/publi/num_WEB.pdf
| access-date=2014-03-27
| archive-date=2016-03-28
| archive-url=https://web.archive.org/web/20160328145817/http://lacito.vjf.cnrs.fr/documents/publi/num_WEB.pdf
| url-status=dead
}}</ref> are known to use duodecimal numerals.

[[Germanic languages]] have special words for 11 and 12, such as ''eleven'' and ''twelve'' in [[English language|English]]. They come from [[Proto-Germanic]] *''ainlif'' and *''twalif'' (meaning, respectively, ''one left'' and ''two left''), suggesting a decimal rather than duodecimal origin.<ref>{{cite book|last=von Mengden| first=Ferdinand| date=2006|chapter=The peculiarities of the Old English numeral system |title=Medieval English and its Heritage: Structure Meaning and Mechanisms of Change|editor1=Nikolaus Ritt |editor2=Herbert Schendl |editor3=Christiane Dalton-Puffer |editor4=Dieter Kastovsky|publisher=Peter Lang |series=Studies in English Medieval Language and Literature |volume=16 |location=Frankfurt |pages= 125–145}}</ref><ref>{{cite book|last=von Mengden |first=Ferdinand |date=2010| title=Cardinal Numerals: Old English from a Cross-Linguistic Perspective |series=Topics in English Linguistics | volume=67|location= Berlin; New York|publisher=De Gruyter Mouton| pages=159–161}}</ref> However, [[Old Norse]] used a hybrid decimal–duodecimal counting system, with its words for "one hundred and eighty" meaning 200 and "two hundred" meaning 240.<ref>{{cite book|last=Gordon|first=E V|title=Introduction to Old Norse|year=1957|publisher=Clarendon Press|location=Oxford|pages=292–293}}</ref> In the British Isles, this style of counting survived well into the Middle Ages as the [[long hundred]] ("hundred" meaning 120).

Historically, [[Unit of time|units of time]] in many [[civilization]]s are duodecimal. There are twelve signs of the [[zodiac]], twelve months in a year, and the [[Babylonians]] had twelve hours in a day (although at some point, this was changed to 24). Traditional [[Chinese calendar]]s, clocks, and compasses are based on the twelve [[Earthly Branches]] or 24 (12×2) [[Solar term]]s. There are 12&nbsp;inches in an imperial foot, 12&nbsp;[[troy weight|troy]] ounces in a troy pound, 24&nbsp;(12×2) hours in a day; many other items are counted by the [[dozen]], [[gross (unit)|gross]] (144, twelve [[Square (algebra)|squared]]), or [[great gross]] (1728, twelve [[Cube (algebra)|cubed]]). The Romans used a fraction system based on 12, including the [[uncia (length)|uncia]], which became both the English words ''[[ounce]]'' and ''inch''. Historically, many parts of western Europe used a mixed [[vigesimal]]–duodecimal currency system of [[£sd|pounds, shillings, and pence]], with 20 shillings to a pound and 12 pence to a shilling, [[Carolingian monetary system|originally established]] by [[Charlemagne]] in the 780s.

{| class="wikitable" style=text-align:center
|+ Duodecimally divided units
|-
! rowspan=2 | Relative<br>value
! colspan=2 | Length
! colspan=2 | Weight
|-
! French
! English
! English (Troy)
! Roman
|-
|12<sup>0</sup>
|[[Units of measurement in France before the French Revolution#Length|pied]]
|[[Foot (unit)|foot]]
|[[Troy weight#Units of measurement|pound]]
|[[Ancient Roman units of measurement#Weight|libra]]
|-
|12<sup>−1</sup>
|[[Units of measurement in France before the French Revolution#Length|pouce]]
|[[inch]]
|[[Troy weight#Units of measurement|ounce]]
|[[Ancient Roman units of measurement#Weight|uncia]]
|-
|12<sup>−2</sup>
|[[Units of measurement in France before the French Revolution#Length|ligne]]
|[[Line (unit)|line]]
|2 [[Apothecaries' system#English-speaking countries|scruples]]
|2 [[scrupulum|scrupula]]
|-
|12<sup>−3</sup>
|[[Point (typography)#Truchet|point]]
|[[Point (typography)#Truchet|point]]
|[[siliqua|seed]]
|[[siliqua]]
|}