Is there a reason why numbers in Japanese are delimited into blocks of four?


As I understand, Japanese numbers are divided into blocks of four, so while we
would think of the number 89123889 as 89,123,889, in Japan they would think of
it as 8912,3889 (八千九百十二万三千八百八十九). So English uses thousands and Japanese uses
tens of thousands.

Is there any particular reason for this? Not that it matters either way, I'm
just wondering at what point either culture chose to delimit numbers by
thousands, or tens of thousands.

If you reply with Japanese, please use hiragana and furigana only, except for
number kanji.




The following is a summary of [this Wikipedia
article](http://ja.wikipedia.org/wiki/%E5%91%BD%E6%95%B0%E6%B3%95).

A math book called 塵劫記【じんこうき】, published in 1627, was the first book that
described (and probably defined) how to count large numbers in Japanese.

In the [first edition of the
book](http://dbr.library.tohoku.ac.jp/infolib/user_contents/wasan/l/j001/06/j001060007l.png),
there was no "4-digit grouping" as we know today, at least for relatively
small numbers (smaller than 1 極【ごく】). A different kanji was assigned to each
digit. 104 was 万, 105 was 億, 106 was 兆 ... and so on, until it reached 1 極,
which was only(?) 1015.

Soon after that, the 4-digit grouping was introduced in a revised edition of
塵劫記 published in 1631, and 1 極 became 1048. In this edition, 8-digit grouping
was still used for numbers larger than 1 極 (100000000 極 = 1 恒河沙【こうがしゃ】,
100000000 恒河沙 = 1 阿僧祇【あそうぎ】, and so on)

In the [year 1634 edition](http://mahoroba.lib.nara-
wu.ac.jp/y05/html/380/l/p006.html), the 8-digit grouping was completely
removed, and the simple 4-digit grouping system after 万(=104) remained. This
is exactly how the Japanese language count large numbers today.

Before 塵劫記, Japanese had a relatively [small
vocabulary](http://www.sf.airnet.ne.jp/ts/language/number/ancient_japanesej.html)
for big numbers, and 万【よろづ】 (=104) seems to have been the largest unit.
八百万【やおよろづ】 meant "countless."

This 4-digit loop was borrowed from Chinese numeric system. Korea also uses a
similar system. However I couldn't find why and when the Chinese language
started to use the 4-digit scale instead of 3.

(By the way, I was surprised to find that English-speaking people used [long
(6-digit) scale](http://en.wikipedia.org/wiki/Long_and_short_scales) until
relatively recently.)




The following is a summary of [this Wikipedia
article](http://ja.wikipedia.org/wiki/%E5%91%BD%E6%95%B0%E6%B3%95).

A math book called 塵劫記【じんこうき】, published in 1627, was the first book that
described (and probably defined) how to count large numbers in Japanese.

In the [first edition of the
book](http://dbr.library.tohoku.ac.jp/infolib/user_contents/wasan/l/j001/06/j001060007l.png),
there was no "4-digit grouping" as we know today, at least for relatively
small numbers (smaller than 1 極【ごく】). A different kanji was assigned to each
digit. 104 was 万, 105 was 億, 106 was 兆 ... and so on, until it reached 1 極,
which was only(?) 1015.

Soon after that, the 4-digit grouping was introduced in a revised edition of
塵劫記 published in 1631, and 1 極 became 1048. In this edition, 8-digit grouping
was still used for numbers larger than 1 極 (100000000 極 = 1 恒河沙【こうがしゃ】,
100000000 恒河沙 = 1 阿僧祇【あそうぎ】, and so on)

In the [year 1634 edition](http://mahoroba.lib.nara-
wu.ac.jp/y05/html/380/l/p006.html), the 8-digit grouping was completely
removed, and the simple 4-digit grouping system after 万(=104) remained. This
is exactly how the Japanese language count large numbers today.

Before 塵劫記, Japanese had a relatively [small
vocabulary](http://www.sf.airnet.ne.jp/ts/language/number/ancient_japanesej.html)
for big numbers, and 万【よろづ】 (=104) seems to have been the largest unit.
八百万【やおよろづ】 meant "countless."

This 4-digit loop was borrowed from Chinese numeric system. Korea also uses a
similar system. However I couldn't find why and when the Chinese language
started to use the 4-digit scale instead of 3.

(By the way, I was surprised to find that English-speaking people used [long
(6-digit) scale](http://en.wikipedia.org/wiki/Long_and_short_scales) until
relatively recently.)

