Editing Roman numerals (section)

===Standard form===
The following table displays how Roman numerals are usually written in modern times:<ref>{{Cite book |last1=Reddy |first1=Indra K. |url=https://books.google.com/books?id=U3QY7gz0C2cC |title=Essential Math and Calculations for Pharmacy Technicians |last2=Khan |first2=Mansoor A. |date=2003 |publisher=CRC Press |isbn=978-0-203-49534-6 |page=3 |chapter=1 (Working with Arabic and Roman numerals) |quote="Table 1-1 Roman and Arabic numerals (table very similar to the table here, apart from inclusion of Vinculum notation."}}</ref><br>
{| class="wikitable"
|+ Individual decimal places
|-
!   !! Thousands  !! Hundreds    !! Tens        !! Units
|-
| 1 || {{rn|M}}   || {{rn|C}}    || {{rn|X}}    || {{rn|I}}
|-
| 2 || {{rn|MM}}  || {{rn|CC}}   || {{rn|XX}}   || {{rn|II}}
|-
| 3 || {{rn|MMM}} || {{rn|CCC}}  || {{rn|XXX}}  || {{rn|III}}
|-
| 4 ||            || {{rn|CD}}   || {{rn|XL}}   || {{rn|IV}}
|-
| 5 ||            || {{rn|D}}    || {{rn|L}}    || {{rn|V}}
|-
| 6 ||            || {{rn|DC}}   || {{rn|LX}}   || {{rn|VI}}
|-
| 7 ||            || {{rn|DCC}}  || {{rn|LXX}}  || {{rn|VII}}
|-
| 8 ||            || {{rn|DCCC}} || {{rn|LXXX}} || {{rn|VIII}}
|-
| 9 ||            || {{rn|CM}}   || {{rn|XC}}   || {{rn|IX}}
|}

{{anchor|Subtractive notation<!--[[Sign-value notation]] links to this anchor; please update that article if this anchor is changed or deleted.-->}} The numerals for 4 ({{rn|IV}}) and 9 ({{rn|IX}}) are written using [[subtractive notation]],<ref name="deha1997">{{Cite book |last=Dehaene |first=Stanislas |title=The Number Sense : How the Mind Creates Mathematics |date=1997 |publisher=Oxford University Press |isbn=9780199723096}} 288 pages.</ref> where the smaller symbol ({{rn|I}}) is ''subtracted'' from the larger one ({{rn|V}}, or {{rn|X}}), thus avoiding the clumsier {{rn|IIII}} and {{rn|VIIII}}.{{efn|Without theorising about causation, it may be noted that {{rn|IV}} and {{rn|IX}} not only have fewer characters than {{rn|IIII}} and {{rn|VIIII}}, but are less likely to be confused (especially at a quick glance) with {{rn|III}} and {{rn|VIII}}.}} Subtractive notation is also used for 40 ({{rn|XL}}), 90 ({{rn|XC}}), 400 ({{rn|CD}}) and 900 ({{rn|CM}}).<ref name="ema1990">{{Cite encyclopedia |title=Numbers, Representations of |encyclopedia=Encyclopaedia of Mathematics |publisher=Springer |url=https://books.google.com/books?id=kwMdtnhtUMMC&dq=%22Roman+numerals%22+additive&pg=PA502 |date=1990 |editor-last=Hazewinkel |editor-first=Michiel |volume=6 |page=502 |isbn=9781556080050}} 546 pages.</ref> These are the only subtractive forms in standard use.

A number containing two or more decimal digits is built by appending the Roman numeral equivalent for each, from highest to lowest, as in the following examples:
* &nbsp;&numsp;&numsp;39 = {{rn|XXX}} + {{rn|IX}} = '''{{rn|XXXIX}}'''.
* &nbsp;&numsp;246 = {{rn|CC}} + {{rn|XL}} + {{rn|VI}} = '''{{rn|CCXLVI}}'''.
* &nbsp;&numsp;789 = {{rn|DCC}} + {{rn|LXXX}} + {{rn|IX}} = '''{{rn|DCCLXXXIX}}'''.
* 2,421 = {{rn|MM}} + {{rn|CD}} + {{rn|XX}} + {{rn|I}} = '''{{rn|MMCDXXI}}'''.

Any missing place (represented by a zero in the place-value equivalent) is omitted, as in Latin (and English) speech:
* &nbsp;&numsp;160 = {{rn|C}} + {{rn|LX}} = '''{{rn|CLX}}'''
* &nbsp;&numsp;207 = {{rn|CC}} + {{rn|VII}} = '''{{rn|CCVII}}'''
* 1,009 = {{rn|M}} + {{rn|IX}} = '''{{rn|MIX}}'''
* 1,066 = {{rn|M}} + {{rn|LX}} + {{rn|VI}} = '''{{rn|MLXVI}}'''<ref>{{Cite book |last1=Dela Cruz |first1=M. L. P. |url=https://books.google.com/books?id=PVK6lt2xXz4C |title=Number Smart Quest for Mastery: Teacher's Edition |last2=Torres |first2=H. D. |date=2009 |publisher=Rex Bookstore, Inc. |isbn=9789712352164}}</ref><ref name="martelli">{{Cite book |last1=Martelli |first1=Alex |url=https://archive.org/details/pythoncookbook00mart |title=Python Cookbook |last2=Ascher |first2=David |date=2002 |publisher=O'Reilly Media Inc. |isbn=978-0-596-00167-4 |url-access=registration}}</ref>

The largest number that can be represented in this manner is 3,999 ('''{{rn|MMMCMXCIX}}'''), but this is sufficient for the values for which Roman numerals are commonly used today, such as year numbers:
* 1776 = {{rn|M}} + {{rn|DCC}} + {{rn|LXX}} + {{rn|VI}} = '''{{rn|MDCCLXXVI}}''' (the date written on the book held by the [[Statue of Liberty]]).
* 1918 = {{rn|M}} + {{rn|CM}} + {{rn|X}} + {{rn|VIII}} = '''{{rn|MCMXVIII}}''' (the first year of the [[Spanish flu]] pandemic)
* 1944 = {{rn|M}} + {{rn|CM}} + {{rn|XL}} + {{rn|IV}} = '''{{rn|MCMXLIV}}''' (erroneous copyright notice of the 1954 movie ''[[The Last Time I Saw Paris#Copyright|The Last Time I Saw Paris]]'')<ref name="Hayes" />
* {{#time:Y}} = '''{{rn|{{#time:xrY}}}}''' (this year){{efn|This is the Coordinated Universal Time (UTC) year in which Wikipedia's cache of this page was last updated, so may be a few hours out of date.}}

Prior to the introduction of Arabic numerals in the West, ancient and medieval users of Roman numerals used various means to write larger numbers {{xref|(see {{slink||Large numbers}} below)}}.