Editing Decimal separator (section)

===Hellenistic–Renaissance eras===
{{anchor|Separatrix|Pythagorean arc}}
In the [[Middle Ages]], before printing, a [[overline|bar]] ( ¯ ) over the [[units digit]] was used to separate the integral part of a number from its [[fractional part]], as in 9{{overline|9}}95 (meaning 99.95 in [[decimal]] point format). A similar notation remains in common use as an underbar to superscript digits, especially for monetary values without a decimal separator, as in 99<sup>{{underline|95}}</sup>. Later, a "separatrix" (i.e., a short, roughly vertical ink stroke) between the units and tenths position became the norm among [[Mathematics in medieval Islam|Arab mathematicians]] (e.g. 99'''ˌ'''95), while an L-shaped or [[vertical bar]] ({{!}}) served as the separatrix in England.<ref>{{cite dictionary |dictionary=Oxford English Dictionary |title=separatrix, ''n.'' |place=Oxford, UK |publisher=Oxford University Press }}</ref> When this character was [[typeset]], it was convenient to use the existing [[Comma (punctuation)|comma]] (99''','''95) or [[full stop]] (99'''.'''95) instead.

Positional [[decimal fraction]]s appear for the first time in a book by the Arab mathematician [[Abu'l-Hasan al-Uqlidisi]] written in the 10th century.<ref name=Berggren>{{cite book |first=J. Lennart |last=Berggren |year=2007 |chapter=Mathematics in Medieval Islam |editor-first=Victor J. |editor-last=Katz |title=The Mathematics of Egypt, Mesopotamia, China, India, and Islam: A sourcebook |publisher=Princeton University Press |isbn=978-0-691-11485-9 |page=530 }}</ref> The practice is ultimately derived from the decimal [[Hindu–Arabic numeral system]] used in [[Indian mathematics]],<ref>{{cite book |author1=Reimer, L. |author2=Reimer, W. |title=Mathematicians are People, too: Stories from the lives of great mathematicians |volume=2 |year=1995 |pages=22 |place=Parsippany, NJ |publisher=Pearson Education, / Dale Seymor Publications |isbn=0-86651-823-1}}</ref> and popularized by the [[Persian people|Persian]] mathematician [[Al-Khwarizmi]],<ref>{{cite web |url=http://www.oxfordislamicstudies.com/article/opr/t125/e1305 |archive-url=https://web.archive.org/web/20130618081123/http://www.oxfordislamicstudies.com/article/opr/t125/e1305 |url-status=dead |archive-date=18 June 2013 |title=Khwarizmi, Abu Jafar Muhammad ibn Musa al- |type=biography |website=Oxford Islamic Studies Online}}</ref> when [[Latin]] translation of [[#Arithmetic|his work]] on the [[Indian numerals]] introduced the decimal [[Positional notation|positional number system]] to the Western world. His ''[[Compendious Book on Calculation by Completion and Balancing]]'' presented the first systematic solution of [[linear equation|linear]] and [[quadratic equation]]s in Arabic.

[[Pope Sylvester II|Gerbert of Aurillac]] marked triples of columns with an arc (called a "Pythagorean arc"), when using his Hindu–Arabic numeral-based abacus in the 10th&nbsp;century. [[Fibonacci]] followed this convention when writing numbers, such as in his influential work {{lang|la|[[Liber Abaci]]}} in the 13th&nbsp;century.<ref>{{cite book |last=Devlin |first=Keith |year=2011 |title=The Man of Numbers: Fibonacci's Arithmetic Revolution |publisher=Walker & Company |place=New York, NY |isbn=9780802779083 |pages=[https://archive.org/details/manofnumbersfibo0000devl/page/44 44–45] |url=https://archive.org/details/manofnumbersfibo0000devl |url-access=registration }}</ref> 

The earliest known record of using the decimal point is in the astronomical tables compiled by the Italian merchant and mathematician [[Giovanni Bianchini]] in the 1440s.<ref>{{Cite journal |last=Marchant |first=Jo |date=2024-02-19 |title=The decimal point is 150 years older than historians thought |url=https://www.nature.com/articles/d41586-024-00473-2 |journal=Nature |language=en |doi=10.1038/d41586-024-00473-2|pmid=38374392 |url-access=subscription }}</ref>{{contradict-inline|History of mathematical notation#Indian and Arabic numerals and notation|date=April 2025}}

Tables of [[logarithm]]s prepared by [[John Napier]] in 1614 and 1619 used the period (full stop) as the decimal separator, which was then adopted by [[Henry Briggs (mathematician)|Henry Briggs]] in his influential 17th century work.

In [[France]], the full stop was already in use in printing to make [[Roman numerals]] more readable, so the comma was chosen.<ref name=Santillana-1996>{{cite encyclopedia |encyclopedia=Enciclopedia Universal Santillana |year=1996 |publisher=Santillana S.A. |place=Barcelona, Spain |isbn=84-294-5129-3 |title=Comma |at=def.&nbsp;2 |quote=coma: MAT. Signo utilizado en los números no enteros para separar la parte entera de la parte decimal o fraccionaria; p.&nbsp;ej., {{nobr| 2,123 .}} }}</ref>

Many other countries, such as Italy, also chose to use the comma to mark the decimal units position.<ref name=Santillana-1996/> It has been [[ISO 80000-2|made standard]] by the [[International Organization for Standardization|ISO]] for international blueprints.<ref>{{cite report |title=Quantities and units |section=Part&nbsp;2: Mathematical signs and symbols to be used in the natural sciences and technology |id=ISO 80000-2:2009 |year=2009 |publisher=[[International Organization for Standardization]] |section-url=http://www.iso.org/iso/catalogue_detail?csnumber=31887 |access-date=1 July 2010}}</ref> However, English-speaking countries took the comma to separate sequences of three digits. In some countries, a raised dot or dash (''{{visible anchor|upper comma}}'') may be used for grouping or decimal separator; this is particularly common in handwriting.