5.2. Large numbers


The East Asian number system is based on ten thousand, which means multiplying ten thousand to a unit makes the next unit, while the European number system is based on one thousand, which means multiplying one thousand to a unit makes the next unit, for instance thousand times thousand is a million, and thousand times a million is a billion.

The Japanese units shown below are from Jinkôki, 1634 A.D. edition. There are several less common large number names other than them. The units larger than (ke)(i) "kei" ( 1016 ) are rarely used, like units larger than trillion are rarely used in American English.

UnitJapaneseAmerican English
104
(ma)(n)
man
 ten thousand
108
(o)(ku)
oku
 hundred million
1012
(ti)(small yo)(u)
tyô
 one trillion
1016
(ke)(i)
kei
 ten quadrillion
1020
(ga)(i)
gai
 hundred quintilliton
1024
(zi)(small yo)
zyo
 one septillion
1028
(zi)(small yo)(u)
zyô
 ten octillion
1032
(ko)(u)
kô
 hundred nonillion
1036
(ka)(n)
kan
 one undecillion
1040
(se)(i)
sei
 ten duodecillion
1044
(sa)(i)
sai
 hundred tredecillion
1048
(go)(ku)
goku
 one quindecillion
1052
(go)(u)(ga)(si)(small ya)
gôgasya
 ten sexdecillion
1056
(a)(so)(u)(gi)
asôgi
 hundred septendecillion
1060
(na)(yu)(ta)
nayuta
 one novemdecillion
1064
(hu)(ka)(si)(gi)
hukasigi
 ten vigintillion
1068
(mu)(ri)(small yo)(u)(ta)(i)(su)(u)
muryôtaisû
 hundred unvigintillion


Reading large numbers in Japanese may be awkward if your native language uses a system based on one thousand. To read large numbers in Japanese, divide them into four-digit groups, and read the groups separately and add appropriate units. If a four-digit group is zero, omit both the group and the unit. Don't omit a four-digit group even when it is one. For example, number 10000 is pronounced as (i)(ti)(ma)(n) "itiman" (1 × 10000), not just (ma)(n) "man".

Since digits should be divided into four-digit groups in Asian number system, commas for every three digits in English are not useful at all. But Japanese people do use a comma (not Japanese comma but European comma) for every three digits, not for every four digits.

The units of big numbers affect the phonemes of the last mora of the preceding four-digit group. See the euphonic change rules of small numbers.

Here is a big number example. Blue letters indicate changed phonemes.
Number 9784510283700004037 is pronounced as follows:

GroupDigits and units
0978
( 9 × 100+7 × 10+8 ) × 1016
(ki)(small yu)(u)(hi)(small ya)(ku)(na)(na)(zi)(small yu)(u)(ha)(small tu)(ke)(i)
kyûhyakunanazyûhakkei
4510
( 4 × 1000+5 × 100+10 ) × 1012
(yo)(n)(se)(n)(go)(hi)(small ya)(ku)(zi)(small yu)(small tu)(ti)(small yo)(u)
yonsengohyakuzyuttyô
2837
( 2 × 1000+8 × 100+3 × 10+7 ) × 108
(ni)(se)(n)(ha)(small tu)(pi)(small ya)(ku)(sa)(n)(zi)(small yu)(u)(na)(na)(o)(ku)
nisenhappyakusanzyûnanaoku
0000 -
4037
4 × 1000+3 × 10+7
(yo)(n)(se)(n)(sa)(n)(zi)(small yu)(u)(na)(na)
yonsensanzyûnana

The result is (ki)(small yu)(u)(hi)(small ya)(ku) (na)(na)(zi)(small yu)(u) (ha)(small tu)(ke)(i) (yo)(n)(se)(n) (go)(hi)(small ya)(ku) (zi)(small yu)(small tu)(ti)(small yo)(u) (ni)(se)(n) (ha)(small tu)(pi)(small ya)(ku) (sa)(n)(zi)(small yu)(u) (na)(na)(o)(ku) (yo)(n)(se)(n) (sa)(n)(zi)(small yu)(u) (na)(na) "kyûhyaku nanazyû hakkei yonsen gohyaku zyuttyô nisen happyaku sanzyû nanaoku yonsen sanzyû nana".


These are Japanese translations of American English large numbers.

UnitAmerican EnglishJapanese
103 one thousand
(se)(n)
sen
106 one million
(hi)(small ya)(ku)(ma)(n)
hyakuman
109 one billion
(zi)(small yu)(u)(o)(ku)
zyûoku
1012 one trillion
(i)(small tu)(ti)(small yo)(u)
ittyô
1015 one quadrillion
(se)(n)(ti)(small yo)(u)
sentyô
1018 one quintillion
(hi)(small ya)(small tu)(ke)(i)
hyakkei
1021 one sextillion
(zi)(small yu)(u)(ga)(i)
zyûgai
1024 one septillion
(i)(ti)(zi)(small yo)
ichizyo
1027 one octillion
(se)(n)(zi)(small yo)
senzyo
1030 one nonillion
(hi)(small ya)(ku)(zi)(small yo)(u)
hyakuzyô
1033 one decillion
(zi)(small yu)(small tu)(ko)(u)
zyukkô
1036 one undecillion
(i)(small tu)(ka)(n)
ikkan
1039 one duodecillion
(se)(n)(ka)(n)
senkan
1042 one tredecillion
(hi)(small ya)(ku)(se)(i)
hyakusei
1045 one quattuordecillion
(zi)(small yu)(small tu)(sa)(i)
zyussai
1048 one quindecillion
(i)(ti)(go)(ku)
itigoku
1051 one sexdecillion
(se)(n)(go)(ku)
sengoku
1054 one septendecillion
(hi)(small ya)(ku)(go)(u)(ga)(si)(small ya)
hyakugôgasya
1057 one octodecillion
(zi)(small yu)(u)(a)(so)(u)(gi)
zyûasôgi
1060 one novemdecillion
(i)(ti)(na)(yu)(ta)
itinayuta
1063 one vigintillion
(se)(n)(na)(yu)(ta)
sennayuta
1066 one unvigintillion
(hi)(small ya)(ku)(hu)(ka)(si)(gi)
hyakuhukasigi
1069 one duovigintillion
(zi)(small yu)(u)(mu)(ri)(small yo)(u)(ta)(i)(su)(u)
zyûmuryôtaisû



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