Editing English numerals (section)

===Very large numbers===
For numbers above a million, there are three main systems used to form numbers in English. (For the use of prefixes such as kilo- for a thousand, mega- for a million, milli- for a thousandth, etc. see [[SI units]].) These are:
*the [[long and short scales|long scale]] – designates a system of numeric names formerly used in British English, but now obsolete, in which a ''billion'' is used for a million million (and similarly, with trillion, quadrillion etc., the prefix denoting the power of a million); and a thousand million is sometimes called a ''milliard''. This system is still used in several other European languages. There is some favour for this scale in astronomy, due to the issue of the vastness of the Universe.
*the [[long and short scales|short scale]] – always used in American English and almost always in British English since the politically-ordained{{fact|date=October 2024}} formal adoption of this scale in the 1970s – designates a system of numeric names in which a thousand million is called a ''billion'', and the word ''milliard'' is not used.
*the [[Indian numbering system]], used widely across [[Indian subcontinent]].

Many people have no direct experience of manipulating numbers this large, and many non-American readers may interpret ''billion'' as 10<sup>12</sup> (even if they are young enough to have been taught otherwise at school); moreover, usage of the "long" billion is standard in some non-English-speaking countries. For these reasons, defining the word may be advisable when writing for the public.

{|class="wikitable"
!Number notation
!Power<br />notation
!Short scale
!Long scale
!Indian<br />(or South Asian) English
|-
|1,000,000||10<sup>6</sup>
|one [[million]]
|one million
|ten lakh
|-
|1,000,000,000||10<sup>9</sup>
|one [[1,000,000,000 (number)|billion]]<br />''a thousand million''
|one [[milliard]]<br />''a thousand million''
|one hundred crore<br />(one ''[[South Asian numbering system|arab]]'')
|-
|1,000,000,000,000||10<sup>12</sup>
|one [[Orders of magnitude (numbers)#1012|trillion]]<br />''a thousand billion''
|one [[1,000,000,000,000 (number)|billion]]<br />''a million million''
|one lakh crore<br />(ten ''[[South Asian numbering system|kharab]]'')
|-
|1,000,000,000,000,000||10<sup>15</sup>
|one [[1,000,000,000,000,000|quadrillion]]<br />''a thousand trillion''
|one [[Billiard (number)|billiard]]<br />''a thousand billion''
|ten crore crore<br />(one ''[[South Asian numbering system|padm]]'')
|-
|1,000,000,000,000,000,000||10<sup>18</sup>
|one [[quintillion]]<br />''a thousand quadrillion''
|one [[Orders of magnitude (numbers)#1018|trillion]]<br />''a million billion''
|ten thousand crore crore<br />(ten ''[[South Asian numbering system|shankh]]'')
|-
|1,000,000,000,000,000,000,000||10<sup>21</sup>
|one [[sextillion]]<br />''a thousand quintillion''
|one [[trilliard]]<br />''a thousand trillion''
|one crore crore crore
|}

The numbers past one trillion in the short scale, in ascending powers of 1000, are as follows: quadrillion, quintillion, sextillion, septillion, octillion, nonillion, decillion, undecillion, duodecillion, tredecillion, quattuordecillion, quindecillion, sexdecillion, septendecillion, octodecillion, novemdecillion and vigintillion (which is 10 to the 63rd power, or a one followed by 63 zeros). The highest number in this series listed in modern dictionaries is centillion, which is 10 to the 303rd power.<ref>''[[Webster's Third New International Dictionary]], Unabridged'', 1993, Merriam-Webster</ref>  The interim powers of one thousand between vigintillion and centillion do not have standardized names, nor do any higher powers, but there are many {{Lang|la|ad hoc}} extensions in use. The highest number listed in Robert Munafo's table of such unofficial names<ref>{{cite web|url=http://www.mrob.com/pub/math/largenum.html|title=Large Numbers at MROB}}</ref> is milli-millillion, which was coined as a name for 10 to the 3,000,003rd power.

The [[googolplex]] was often cited as the largest named number in English. If a [[googol]] is ten to the one hundredth power, then a googolplex is one followed by a googol of zeros (that is, ten to the power of a googol).<ref>{{cite web|url=http://ask.yahoo.com/20051018.html|title=Home - Yahoo Answers}}</ref> There is the coinage, of very little use, of ten to the googolplex power, of the word [[wikt:googolplexplex|googolplexplex]].

The terms ''arab'', ''kharab'', ''padm'' and ''shankh'' are more commonly found in old books on Indian mathematics.

Here are some approximate composite large numbers in American English:
{|class="wikitable"
|-
!Quantity
!Written
!Pronounced
|-
|1,200,000||1.2 [[million]]||one point two million
|-
|3,000,000||3 million||three million
|-
|250,000,000||250 million||two hundred fifty million
|-
|6,400,000,000||6.4 billion||six point four billion
|-
|23,380,000,000||23.38 billion||twenty-three point three eight billion
|}

Often, large numbers are written with (preferably [[non-breaking]]) [[half-space (punctuation)|half-space]]s or thin spaces separating the thousands (and, sometimes, with normal [[space]]s or [[apostrophe (mark)|apostrophe]]s) instead of [[comma (punctuation)|comma]]s&mdash;to ensure that confusion is not caused in countries where a [[decimal comma]] is used. Thus, a million is often written 1&nbsp;000&nbsp;000. In some areas, a [[point (typography)|point]] (. or ·) may also be used as a [[thousands separator]], but then the [[decimal separator]] must be a comma (,). In English the point (.) is used as the decimal separator, and the comma (,) as the thousands separator.