Depending on context (i.e. language, culture, region, ...) some large numbers have names that allow for describing large quantities in a textual form; not mathematical. For very large values, the text is generally shorter than a decimal numeric representation although longer than scientific notation.

Two naming scales for large numbers have been used in English and other European languages since the early modern era: the long and short scales. Most English variants use the short scale today, but the long scale remains dominant in many non-English-speaking areas, including continental Europe and Spanish-speaking countries in Latin America. These naming procedures are based on taking the number n occurring in 10 (short scale) or 10 (long scale) and concatenating Latin roots for its units, tens, and hundreds place, together with the suffix -illion.

Names of numbers above a trillion are rarely used in practice; such large numbers have practical usage primarily in the scientific domain, where powers of ten are expressed as 10 with a numeric superscript. However, these somewhat rare names are considered acceptable for approximate statements. For example, the statement "There are approximately 7.1 octillion atoms in an adult human body" is understood to be in short scale of the table below (and is only accurate if referring to short scale rather than long scale).

The Indian numbering system uses the named numbers common between the long and short scales up to ten thousand. For larger values, it includes named numbers at each multiple of 100; including lakh (10) and crore (10).

English also has words, such as zillion, that are used informally to mean large but unspecified amounts.

x	Name (SS/LS, LS)	SS (10)	LS (10, 10)	Authorities
				AHD4	CED	COD	OED2	OEDweb	RHD2	SOED3	W3	HM
1	Million	10	10	✓	✓	✓	✓	✓	✓	✓	✓	✓
	Milliard		10	✓	✓	✓	✓	✓	✓			✓
2	Billion	10	10	✓	✓	✓	✓	✓	✓	✓	✓	✓
3	Trillion	10	10	✓	✓	✓	✓	✓	✓	✓	✓	✓
4	Quadrillion	10	10	✓	✓	✓	✓	✓	✓	✓	✓	✓
5	Quintillion	10	10	✓	✓	✓	✓	✓	✓	✓	✓	✓
6	Sextillion	10	10	✓	✓		✓	✓	✓	✓	✓	✓
7	Septillion	10	10	✓	✓		✓	✓	✓	✓	✓	✓
8	Octillion	10	10	✓	✓		✓	✓	✓	✓	✓	✓
9	Nonillion	10	10	✓	✓		✓	✓	✓	✓	✓	✓
10	Decillion	10	10	✓	✓		✓	✓	✓	✓	✓	✓
11	Undecillion	10	10	✓	✓				✓		✓	✓
12	Duodecillion	10	10	✓	✓	✓			✓		✓	✓
13	Tredecillion	10	10	✓	✓				✓		✓	✓
14	Quattuordecillion	10	10	✓	✓				✓		✓	✓
15	Quindecillion	10	10	✓	✓				✓		✓	✓
16	Sexdecillion	10	10	✓	✓				✓		✓	✓
17	Septendecillion	10	10	✓	✓				✓		✓	✓
18	Octodecillion	10	10	✓	✓				✓		✓	✓
19	Novemdecillion	10	10	✓	✓				✓		✓	✓
20	Vigintillion	10	10	✓	✓		✓	✓	✓	✓	✓	✓
100	Centillion	10	10	✓	✓		✓	✓	✓			✓

Usage:

• Short scale: US, English Canada, modern British, Australia, and Eastern Europe
• Long scale: French Canada, older British, Western & Central Europe

Apart from million, the words in this list ending with -illion are all derived by adding prefixes (bi-, tri-, etc., derived from Latin) to the stem -illion. Centillion appears to be the highest name ending in -"illion" that is included in these dictionaries. Trigintillion, often cited as a word in discussions of names of large numbers, is not included in any of them, nor are any of the names that can easily be created by extending the naming pattern (unvigintillion, duovigintillion, duo­quinqua­gint­illion, etc.).

Name	Value	Authorities
		AHD4	CED	COD	OED2	OEDweb	RHD2	SOED3	W3	HM
Googol	10	✓	✓	✓	✓	✓	✓	✓	✓	✓
Googolplex	10 (10)	✓	✓	✓	✓	✓	✓	✓	✓	✓

All of the dictionaries included googol and googolplex, generally crediting it to the Kasner and Newman book and to Kasner's nephew (see below). None include any higher names in the googol family (googolduplex, etc.). The Oxford English Dictionary comments that googol and googolplex are "not in formal mathematical use".

Some names of large numbers, such as million, billion, and trillion, have real referents in human experience, and are encountered in many contexts, particularly in finance and economics. At times, the names of large numbers have been forced into common usage as a result of hyperinflation. The highest numerical value banknote ever printed was a note for 1 sextillion pengő (10 or 1 milliard bilpengő as printed) printed in Hungary in 1946. In 2009, Zimbabwe printed a 100 trillion (10) Zimbabwean dollar note, which at the time of printing was worth about US$30. In global economics, the name of a significantly larger number was used in 2024, when the Russian news outlet RBK stated that the sum of legal claims against Google in Russia totalled 2 undecillion (2×10) rubles, or US $20 decillion (US $2×10); a value worth more than all financial assets in the world combined. A Kremlin spokesperson, Dmitry Peskov, stated that this value was symbolic.

Names of larger numbers, however, have a tenuous, artificial existence, rarely found outside definitions, lists, and discussions of how large numbers are named. Even well-established names like sextillion are rarely used, since in the context of science, including astronomy, where such large numbers often occur, they are nearly always written using scientific notation. In this notation, powers of ten are expressed as 10 with a numeric superscript, e.g. "The X-ray emission of the radio galaxy is 1.3×10 joules." When a number such as 10 needs to be referred to in words, it is simply read out as "ten to the forty-fifth" or "ten to the forty-five". This is easier to say and less ambiguous than "quattuordecillion", which means something different in the long scale and the short scale.

When a number represents a quantity rather than a count, SI prefixes can be used—thus "femtosecond", not "one quadrillionth of a second"—although often powers of ten are used instead of some of the very high and very low prefixes. In some cases, specialized units are used, such as the astronomer's parsec and light year or the particle physicist's barn.

Nevertheless, large numbers have an intellectual fascination and are of mathematical interest, and giving them names is one way people try to conceptualize and understand them.

One of the earliest examples of this is The Sand Reckoner, in which Archimedes gave a system for naming large numbers. To do this, he called the numbers up to a myriad myriad (10) "first numbers" and called 10 itself the "unit of the second numbers". Multiples of this unit then became the second numbers, up to this unit taken a myriad myriad times, 10·10=10. This became the "unit of the third numbers", whose multiples were the third numbers, and so on. Archimedes continued naming numbers in this way up to a myriad myriad times the unit of the 10-th numbers, i.e. ${\displaystyle (10^{8})^{(10^{8})}=10^{8\cdot 10^{8}},}$ and embedded this construction within another copy of itself to produce names for numbers up to ${\displaystyle ((10^{8})^{(10^{8})})^{(10^{8})}=10^{8\cdot 10^{16}}.}$ Archimedes then estimated the number of grains of sand that would be required to fill the known universe, and found that it was no more than "one thousand myriad of the eighth numbers" (10).

Since then, many others have engaged in the pursuit of conceptualizing and naming numbers that have no existence outside the imagination. One motivation for such a pursuit is that attributed to the inventor of the word googol, who was certain that any finite number "had to have a name". Another possible motivation is competition between students in computer programming courses, where a common exercise is that of writing a program to output numbers in the form of English words.

Most names proposed for large numbers belong to systematic schemes which are extensible. Thus, many names for large numbers are simply the result of following a naming system to its logical conclusion—or extending it further.

The words bymillion and trimillion were first recorded in 1475 in a manuscript of Jehan Adam. Subsequently, Nicolas Chuquet wrote a book Triparty en la science des nombres which was not published during Chuquet's lifetime. However, most of it was copied by Estienne de La Roche for a portion of his 1520 book, L'arismetique. Chuquet's book contains a passage in which he shows a large number marked off into groups of six digits, with the comment:

Ou qui veult le premier point peult signiffier million Le second point byllion Le tiers point tryllion Le quart quadrillion Le cinq quyllion Le six sixlion Le sept. septyllion Le huyt ottyllion Le neuf nonyllion et ainsi des ault' se plus oultre on vouloit preceder

(Or if you prefer the first mark can signify million, the second mark byllion, the third mark tryllion, the fourth quadrillion, the fifth quyillion, the sixth sixlion, the seventh septyllion, the eighth ottyllion, the ninth nonyllion and so on with others as far as you wish to go).

Adam and Chuquet used the long scale of powers of a million; that is, Adam's bymillion (Chuquet's byllion) denoted 10, and Adam's trimillion (Chuquet's tryllion) denoted 10.

The names googol and googolplex were invented by Edward Kasner's nephew Milton Sirotta and introduced in Kasner and Newman's 1940 book Mathematics and the Imagination in the following passage:

The name "googol" was invented by a child (Dr. Kasner's nine-year-old nephew) who was asked to think up a name for a very big number, namely 1 with one hundred zeroes after it. He was very certain that this number was not infinite, and therefore equally certain that it had to have a name. At the same time that he suggested "googol" he gave a name for a still larger number: "googolplex". A googolplex is much larger than a googol, but is still finite, as the inventor of the name was quick to point out. It was first suggested that a googolplex should be 1, followed by writing zeros until you got tired. This is a description of what would happen if one tried to write a googolplex, but different people get tired at different times and it would never do to have Carnera a better mathematician than Dr. Einstein, simply because he had more endurance. The googolplex is, then, a specific finite number, equal to 1 with a googol zeros after it.

Value	Name	Authority
10	Googol	Kasner and Newman, dictionaries (see above)
10 = 10	Googolplex	Kasner and Newman, dictionaries (see above)

John Horton Conway and Richard K. Guy have suggested that N-plex be used as a name for 10. This gives rise to the name googolplexplex for 10 = 10. Conway and Guy have proposed that N-minex be used as a name for 10, giving rise to the name googolminex for the reciprocal of a googolplex, which is written as 10). None of these names are in wide use.

The names googol and googolplex inspired the name of the Internet company Google and its corporate headquarters, the Googleplex, respectively.

This section illustrates several systems for naming large numbers, and shows how they can be extended past vigintillion.

Traditional British usage assigned new names for each power of one million (the long scale): 1,000,000 = 1 million; 1,000,000 = 1 billion; 1,000,000 = 1 trillion; and so on. It was adapted from French usage, and is similar to the system that was documented or invented by Chuquet.

Traditional American usage (which was also adapted from French usage but at a later date), Canadian, and modern British usage assign new names for each power of one thousand (the short scale). Thus, a billion is 1000 × 1000 = 10; a trillion is 1000 × 1000 = 10; and so forth. Due to its dominance in the financial world (and by the US dollar), this was adopted for official United Nations documents.

Traditional French usage has varied; in 1948, France, which had originally popularized the short scale worldwide, reverted to the long scale.

The term milliard is unambiguous and always means 10. It is seldom seen in American usage and rarely in British usage, but frequently in continental European usage. The term is sometimes attributed to French mathematician Jacques Peletier du Mans c. 1550 (for this reason, the long scale is also known as the Chuquet-Peletier system), but the Oxford English Dictionary states that the term derives from post-Classical Latin term milliartum, which became milliare and then milliart and finally our modern term.

Concerning names ending in -illiard for numbers 10, milliard is certainly in widespread use in languages other than English, but the degree of actual use of the larger terms is questionable. The terms "milliardo" in Italian, "Milliarde" in German, "miljard" in Dutch, "milyar" in Turkish, and "миллиард," milliard (transliterated) in Russian, are standard usage when discussing financial topics.

The naming procedure for large numbers is based on taking the number n occurring in 10 (short scale) or 10 (long scale) and concatenating Latin roots for its units, tens, and hundreds place, together with the suffix -illion. In this way, numbers up to 10 = 10 (short scale) or 10 = 10 (long scale) may be named. The choice of roots and the concatenation procedure is that of the standard dictionary numbers if n is 9 or smaller. For larger n (between 10 and 999), prefixes can be constructed based on a system described by Conway and Guy. Today, sexdecillion and novemdecillion are standard dictionary numbers and, using the same reasoning as Conway and Guy did for the numbers up to nonillion, could probably be used to form acceptable prefixes. The Conway–Guy system for forming prefixes:

	Units	Tens	Hundreds
1	Un	Deci	Centi
2	Duo	Viginti	Ducenti
3	Tre	Triginta	Trecenti
4	Quattuor	Quadraginta	Quadringenti
5	Quin	Quinquaginta	Quingenti
6	Se	Sexaginta	Sescenti
7	Septe	Septuaginta	Septingenti
8	Octo	Octoginta	Octingenti
9	Nove	Nonaginta	Nongenti

^ When preceding a component marked or , "tre" changes to "tres" and "se" to "ses" or "sex"; similarly, when preceding a component marked or , "septe" and "nove" change to "septem" and "novem" or "septen" and "noven".

Since the system of using Latin prefixes will become ambiguous for numbers with exponents of a size which the Romans rarely counted to, like 10, Conway and Guy co-devised with Allan Wechsler the following set of consistent conventions that permit, in principle, the extension of this system indefinitely to provide English short-scale names for any integer whatsoever. The name of a number 10, where n is greater than or equal to 1000, is formed by concatenating the names of the numbers of the form 10, where m represents each group of comma-separated digits of n, with each but the last "-illion" trimmed to "-illi-", or, in the case of m = 0, either "-nilli-" or "-nillion". For example, 10, the 1,000,003rd "-illion" number, equals one "millinillitrillion"; 10, the 11,000,670,036th "-illion" number, equals one "undecillinilli­septua­ginta­ses­centilli­sestrigint­illion"; and 10, the 9,876,543,210th "-illion" number, equals one "nonillise­septua­ginta­octingentillitres­quadra­ginta­quingentillideciducent­illion".

The following table shows number names generated by the system described by Conway and Guy for the short and long scales.

Base -illion (short scale)	Base -illion (long scale)	Value	US, Canada and modern British (short scale)	Traditional British (long scale)	Traditional European (Peletier long scale)	SI Symbol	SI Prefix
1	1	10	Million	Million	Million	M	Mega-
2	1	10	Billion	Thousand million	Milliard	G	Giga-
3	2	10	Trillion	Billion	Billion	T	Tera-
4	2	10	Quadrillion	Thousand billion	Billiard	P	Peta-
5	3	10	Quintillion	Trillion	Trillion	E	Exa-
6	3	10	Sextillion	Thousand trillion	Trilliard	Z	Zetta-
7	4	10	Septillion	Quadrillion	Quadrillion	Y	Yotta-
8	4	10	Octillion	Thousand quadrillion	Quadrilliard	R	Ronna-
9	5	10	Nonillion	Quintillion	Quintillion	Q	Quetta-
10	5	10	Decillion	Thousand quintillion	Quintilliard
11	6	10	Undecillion	Sextillion	Sextillion
12	6	10	Duodecillion	Thousand sextillion	Sextilliard
13	7	10	Tredecillion	Septillion	Septillion
14	7	10	Quattuordecillion	Thousand septillion	Septilliard
15	8	10	Quindecillion	Octillion	Octillion
16	8	10	Sedecillion	Thousand octillion	Octilliard
17	9	10	Septendecillion	Nonillion	Nonillion
18	9	10	Octodecillion	Thousand nonillion	Nonilliard
19	10	10	Novendecillion	Decillion	Decillion
20	10	10	Vigintillion	Thousand decillion	Decilliard
21	11	10	Unvigintillion	Undecillion	Undecillion
22	11	10	Duovigintillion	Thousand undecillion	Undecilliard
23	12	10	Tresvigintillion	Duodecillion	Duodecillion
24	12	10	Quattuor­vigint­illion	Thousand duodecillion	Duodecilliard
25	13	10	Quinvigintillion	Tredecillion	Tredecillion
26	13	10	Sesvigintillion	Thousand tredecillion	Tredecilliard
27	14	10	Septemvigintillion	Quattuordecillion	Quattuordecillion
28	14	10	Octovigintillion	Thousand quattuordecillion	Quattuordecilliard
29	15	10	Novemvigintillion	Quindecillion	Quindecillion
30	15	10	Trigintillion	Thousand quindecillion	Quindecilliard
31	16	10	Untrigintillion	Sedecillion	Sedecillion
32	16	10	Duotrigintillion	Thousand sedecillion	Sedecilliard
33	17	10	Trestrigintillion	Septendecillion	Septendecillion
34	17	10	Quattuor­trigint­illion	Thousand septendecillion	Septendecilliard
35	18	10	Quintrigintillion	Octodecillion	Octodecillion
36	18	10	Sestrigintillion	Thousand octodecillion	Octodecilliard
37	19	10	Septentrigintillion	Novendecillion	Novendecillion
38	19	10	Octotrigintillion	Thousand novendecillion	Novendecilliard
39	20	10	Noventrigintillion	Vigintillion	Vigintillion
40	20	10	Quadragintillion	Thousand vigintillion	Vigintilliard
50	25	10	Quinquagintillion	Thousand quinvigintillion	Quinvigintilliard
60	30	10	Sexagintillion	Thousand trigintillion	Trigintilliard
70	35	10	Septuagintillion	Thousand quintrigintillion	Quintrigintilliard
80	40	10	Octogintillion	Thousand quadragintillion	Quadragintilliard
90	45	10	Nonagintillion	Thousand quin­quadra­gint­illion	Quin­quadra­gint­illiard
100	50	10	Centillion	Thousand quinquagintillion	Quinquagintilliard
101	51	10	Uncentillion	Unquinquagintillion	Unquinquagintillion
110	55	10	Decicentillion	Thousand quin­quinqua­gint­illion	Quin­quinqua­gint­illiard
111	56	10	Undecicentillion	Ses­quinqua­gint­illion	Ses­quinqua­gint­illion
120	60	10	Viginticentillion	Thousand sexagintillion	Sexagintilliard
121	61	10	Unviginticentillion	Unsexagintillion	Unsexagintillion
130	65	10	Trigintacentillion	Thousand quinsexagintillion	Quinsexagintilliard
140	70	10	Quadra­gintacent­illion	Thousand septuagintillion	Septuagintilliard
150	75	10	Quinqua­gintacent­illion	Thousand quin­septua­gint­illion	Quin­septua­gint­illiard
160	80	10	Sexagintacentillion	Thousand octogintillion	Octogintilliard
170	85	10	Septuagintacentillion	Thousand quinoctogintillion	Quinoctogintilliard
180	90	10	Octogintacentillion	Thousand nonagintillion	Nonagintilliard
190	95	10	Nonagintacentillion	Thousand quinnonagintillion	Quinnonagintilliard
200	100	10	Ducentillion	Thousand centillion	Centilliard
300	150	10	Trecentillion	Thousand quinqua­gintacent­illion	Quinqua­gintacent­illiard
400	200	10	Quadringentillion	Thousand ducentillion	Ducentilliard
500	250	10	Quingentillion	Thousand quinqua­gintaducent­illion	Quinqua­gintaducent­illiard
600	300	10	Sescentillion	Thousand trecentillion	Trecentilliard
700	350	10	Septingentillion	Thousand quinqua­gintatrecent­illion	Quinqua­gintatrecent­illiard
800	400	10	Octingentillion	Thousand quadringentillion	Quadringentilliard
900	450	10	Nongentillion	Thousand quinqua­ginta­quadringent­illion	Quinqua­ginta­quadringent­illiard
1000	500	10	Millinillion	Thousand quingentillion	Quingentilliard

Value	Name	Equivalent
		US, Canadian and modern British (short scale)	Traditional British (long scale)	Traditional European (Peletier long scale)
10	Googol	Ten duotrigintillion	Ten thousand sedecillion	Ten sedecilliard
10	Googolplex	Ten trilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­trestrigintatrecentilli­duotrigintatrecentillion	Ten thousand milli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentillion	Ten milli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilli­sesexagintasescentilliard

^[1] Googolplex's short scale name is derived from it equal to ten of the 3,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​333,​332nd "-illion"s (This is the value of n when 10 × 10 = 10)

^[2] Googolplex's long scale name (both traditional British and traditional European) is derived from it being equal to ten thousand of the 1,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666,​666th "-illion"s (This is the value of n when 10,000 × 10 = 10).

The International System of Quantities (ISQ) defines a series of prefixes denoting integer powers of 1024 between 1024 and 1024.

Power	Value	ISQ symbol	ISQ prefix
1	1024	Ki	Kibi-
2	1024	Mi	Mebi-
3	1024	Gi	Gibi-
4	1024	Ti	Tebi-
5	1024	Pi	Pebi-
6	1024	Ei	Exbi-
7	1024	Zi	Zebi-
8	1024	Yi	Yobi-