Editing Roman numerals (section)

====''Apostrophus''====
[[File:Westerkerk MDCXXX.jpg|thumb|upright=0.9| "1630" on the [[Westerkerk]] in Amsterdam. "{{rn|M}}" and "{{rn|D}}" are given archaic {{lang|la|apostrophus}} form.]]

Using the {{lang|la|apostrophus}} method,<ref name="merriam-webster">{{Cite web |url=https://www.merriam-webster.com/dictionary/apostrophus |title=Definition of Apostrophus |website=www.merriam-webster.com}}</ref> 500 is written as {{rn|IↃ}}, while 1,000 is written as {{rn|CIↃ}}.<ref name="asimov on numbers 12" /> This system of encasing numbers to denote thousands (imagine the {{rn|C}}s and {{rn|Ↄ}}s as parentheses) had its origins in Etruscan numeral usage.

Each additional set of {{rn|C}} and {{rn|Ↄ}} surrounding {{rn|CIↃ}} raises the value by a factor of ten: {{rn|CCIↃↃ}} represents 10,000 and {{rn|CCCIↃↃↃ}} represents 100,000. Similarly, each additional {{rn|Ↄ}} to the right of {{rn|IↃ}} raises the value by a factor of ten: {{rn|IↃↃ}} represents 5,000 and {{rn|IↃↃↃ}} represents 50,000. Numerals larger than {{rn|CCCIↃↃↃ}} do not occur.<ref name=PropN3218/>

[[File:Roman numerals Bungus 1584-1585.png|thumb|upright=0.9|Page from a 16th-century manual, showing a mixture of {{lang|la|apostrophus}} and {{lang|la|vinculum}} numbers (see in particular the ways of writing 10,000).]]
* '''{{rn|IↃ}}''' = 500 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;'''{{rn|CIↃ}}''' = 1,000
* '''{{rn|IↃↃ}}''' = 5,000 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;'''{{rn|CCIↃↃ}}''' = 10,000
* '''{{rn|IↃↃↃ}}''' = 50,000 &nbsp;&nbsp;&nbsp;'''{{rn|CCCIↃↃↃ}}''' = 100,000

Sometimes {{rn|CIↃ}} (1000) is reduced to {{rn|ↀ}}, {{rn|IↃↃ}} (5,000) to {{rn|ↁ}}; {{rn|CCIↃↃ}} (10,000) to {{rn|ↂ}}; {{rn|IↃↃↃ}} (50,000) to {{rn|ↇ}}; and {{rn|CCCIↃↃↃ}} (100,000) to {{rn|ↈ}}.<ref name="Ifrah2000">{{Cite book |last=Ifrah |first=Georges |title=The Universal History of Numbers: From Prehistory to the Invention of the Computer |date=2000 |publisher=John Wiley & Sons |others=Translated by David Bellos, E. F. Harding, Sophie Wood, Ian Monk}}</ref> It is likely {{rn|IↃ}} (500) reduced to {{rn|D}} and {{rn|CIↃ}} (1000) influenced  the later {{rn|M}}.

[[John Wallis]] is often credited with introducing the symbol for [[infinity]] {{angbr|∞}}, and one conjecture is that he based it on {{rn|ↀ}}, since 1,000 was [[hyperbole|hyperbolically]] used to represent very large numbers.