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

Question

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.

Answer 1

The following is a summary of this Wikipedia article.

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, 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, 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 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 until relatively recently.)

Answer 2

Numbers in English and most "western" languages are still influenced by Roman numerals, where 1000 = M = mille was the largest number that had its own, non-compound name.

Japanese took its numerals originally from Chinese, where there is a separate character for "ten thousand". It also has characters for larger numbers, but groupings of 5 or more are probably less convenient as they are harder to recognize quickly.

However, neither system historically came into being fully complete and used consistently. Both changed through the times and there were conflicting usages for a long time until everyone converged on a standard.

Answer 3

in Japan they would think of it as 8912,3889 (八千九百十二万三千八百八十九).

Just FYI, no one in Japan writes numbers like that. Maybe you can find a museum or similar re-creation that does it when the tourists are watching, but retail, business, banking, government etc. use western formats.

The only place you will regularly see much smaller numbers written in kanji is on restaurant menus and addresses on new years cards, when the writer is going for an old-fashioned look, like Fraktur in Germany:

とんかつ：一千二百円

東京都品川区上町二丁目十七番9号

but the address is much easier to type as 東京都品川区上町2-17-9

If you are learning this archaic writing method for the end purpose of reading pre-Meiji works in the original Klingon, keep studying. If you are learning modern Japanese for the purpose of working in or with Japan, you already know more than you will ever use. Move on to useful things.

Answer 4

More than likely it is borrowed from Chinese.

十 百 万 亿[億] 兆 京

respectively:

10^1, 10^2, 10^4, 10^8, 10^16, 10^32 etc. (goes on until 10^4096 !)

I have seen 亿 and 兆 used in these definitions in modern Chinese and Korean, and certainly 億 in japanese for money e.g. 三億円 meaning 3 x 10^8 yen.

This system of creating a new word whenever the length doubles seems natural, as it is the minimal set of words you need to represent any arbitrarily large number without repeating yourself. It also provides a more unique way to say a number. For example, in english we could say one million billion == 10^15 == one thousand trillion).

This has changed in modern china... 亿，兆，京 now sometimes mean smaller powers in different contexts for convenience. 兆 can mean a megabyte (10^6), e.g. 四十兆 => 40 Megabytes. Not sure if Japanese has this ambiguity, but 千 (10^3) certainly exists and doesn't fit the 'pure' traditional system.

In any case, I have never seen a split into blocks of 4 when writing a number down. But that is the logic that should be used when reading a number out.

That is misleading though, since even larger numbers should be read by recursively bisecting at the highest 10^2^n which fits, and this can get a lot more abstract than simple powers of 10^4. To choose an unrealistic example:

1,000,020,000,304,567 =>

10000200 * 10^8 + 00304567 =>

1000,0200 億 30,4567 =>

(1000 * 10^4 + 0200) 億 + (30 * 10^4 + 4567) =>

(1000 万 200) 億 (30 万 4567) =>

(一千 万 二百）億（三十 万 四千五百六十七）

Please note it is different than just separating with length 4 blocks: 10^12 does not have a unique name, but 10^16 does. So it really is unlike the western system. Blocks are only assigned a new name when they reach twice the length of the last named block. Rather than just 3,6,9,12,15, we have 4,8,16,32.

For negative powers of 10, the western style of 10^-3, 10^-6, 10^-9 is used... (equivalent to milli/micro/nano).

Answer 5

To add to the previous answers, the rule is Arabic numbers for horizontal writing:

123456789

and Chinese numbers for vertical writing.

一
二
三
四
五