Indefinite and fictitious numbers

• In English, some words that have a precise numerical definition are often used indefinitely: couple, 2;[3] dozen, 12; myriad, 10,000.
• In various Middle Eastern traditions, the number 40 is used to express a large but unspecific number,[4][5] as in the Hebrew Bible's "forty days and forty nights", Ali Baba and the Forty Thieves, and the Forty Martyrs of Sebaste.[6][7] This usage is sometimes found in English as well (for example, "forty winks").[8][9]
• In Latin, sescenti (600) was used to mean a very large number, perhaps from the size of a Roman cohort.[10]
• In Arabic, 1001 is used similarly, as in The Book of One Thousand and One Nights (lit. "a thousand nights and one night").[5] Many modern English book titles use this convention as well: 1,001 Uses for ....
• In Japanese, 八千, 8000, is used: 八千草 (lit. 8,000 herbs) means a variety of herbs and 八千代 ( lit. 8,000 generations) means eternity.
• The number 10,000 is used to express an even larger approximate number, as in Hebrew רבבה r^evâvâh,[11] rendered into Greek as μυριάδες, and to English myriad.[12] Similar usage is found in the East Asian 萬 or 万 (lit. 10,000; pinyin: wàn), and the South Asian lakh (lit. 100,000).[13]
• In Irish, 100,000 (céad míle) is used, as in the phrase céad míle fáilte, "a hundred thousand welcomes" or Gabriel Rosenstock's poetic phrase Irish: mo chéad míle grá ("my hundred thousand loves").[14]
• In Welsh, cant a mil, literally "a hundred and thousand", is used to mean a large number in a similar way to English "a hundred and one".[15] It is used in phrases such as cant a mil o bethau i'w wneud "a hundred and one things to do" i.e. "many, many things to do".
• In Swedish, femtioelva is used, meaning "fifty-eleven".
• In Chinese, 十萬八千里; 十万八千里; shí wàn bā qiān lǐ, 108,000 li, means a great distance.
• In Thai, ร้อยแปด (roi paed), means both 108, and miscellaneous, various, plentiful.[16]

Other specific numbers are occasionally used as indefinite as well. English does this with count nouns that refer to numbers: a dozen/dozens, a score/scores, a hundred/hundreds, and similarly thousand, million, billion. Unlike cardinal numbers, these can be pluralized, in which case they require of before the noun (millions of dollars, but five million dollars), and require the indefinite article "a" in the singular (a million letters (indefinite) but one million letters (definite)).

Umpteen, umteen or umpty[17] is an unspecified but large number, used in a humorous fashion or to imply that it is not worth the effort to pin down the actual figure. Despite the -teen ending, which would seem to indicate that it lies between 12 and 20, umpteen can be much larger.

"Umpty" is first attested in 1905, in the expression "umpty-seven", implying that it is a multiple of ten.[18][19] Ump(ty) came from a verbalization of a dash in Morse code.[18]

"Umpteen", adding the ending -teen, as in "thirteen", is first attested in 1918,[20][17][21] and has become by far the most common form.[22]

In Norwegian, ørten is used in a similar way, playing on the numbers from tretten (13) to nitten (19), but often signifying a much larger number.[23]

Words with the suffix -illion (e.g. zillion,[24] gazillion,[25] jillion,[26] squillion,[27] abigajillion) are often used as informal names for unspecified large numbers by analogy to names of large numbers such as million (10⁶), billion (10⁹) and trillion (10¹²).

These words are intended to denote a number that is large enough to be unfathomable and are typically used as hyperbole or for comic effect. They have no precise value or order. They form ordinals and fractions with the usual suffix -th, e.g. "I asked her for the jillionth time", or "-illionaire" to describe a wealthy person.

Sagan's number is the number of stars in the observable universe. It is named in honor of Carl Sagan.[28] This number is reasonably well defined, because it is known what stars are and what the observable universe is, but its value is highly uncertain.

• In 1980, Carl Sagan himself estimated it to be 10 sextillion in short scale (10²²).[29]
• In 2003, it was estimated to be 70 sextillion (7 × 10²²).[30][31]
• In 2010, it was estimated to be 300 sextillion (3 × 10²³).[32] This would equal the number of H₂ molecules in 1 gram of hydrogen.

Sagan's number is to be distinguished from the sagan unit or the humorous use of the term "sagan" to denote any large quantity—specifically, any number of at least four billion, due to Sagan's association with the phrase "billions and billions".[33][34]

• List of unusual units of measurement
• List of humorous units of measurement
• Names of large numbers
• Hair's breadth
• 1000 percent
• Muggeseggele