When is 分 read ぶ instead of ぶん


I had always thought that when you were talking about percentage, fractions,
portions, etc., it was always pronounced **ぶん**. However, I saw its
pronunciation listed as **ぶ** on [Imabi](http://www.imabi.net/numbersix.htm
"Numbers IX"), a renowned website for self-learners. The likelihood of its
being an error was rather low, since the author seemed to really know his
stuff, solid.

On Imabi, a couple of examples were given:

> 五分五分{ごぶごぶ}の確率  
>  九分九厘{くぶくりん}勝てる。  
>  *八九分{はっくぶ}

*Strangely, MS-IME does not show **八九分** for **はっくぶ** , I have to type each kanji separately. Could it be due to its not being an idiom?

The first two seem to be 四字熟語, so I would simply assume the pronunciations are
not up for discussion. However, what about other combinations, such as
**九割九分**? According to this [native
speaker](https://www.reddit.com/r/LearnJapanese/comments/3odrpj/%E3%82%B7%E3%83%84%E3%83%A2%E3%83%B3%E3%83%87%E3%83%BC_shitsumonday_for_the_little_questions_that/
"It's either きゅうわりきゅうぶ...") (ID: ywja):

> It's either きゅうわりきゅうぶ or くわりくぶ. Personally, I find that きゅうわりきゅうぶ is more
> common. Also, it sounds more colloquial and casual to my ears, probably
> because きゅう sounds more casual than く as the reading of 九.

**Question #1.**  
Her/his explanation appears not to be about personal preference, or
regional/dialectic difference. If there is indeed room for variation, as this
person suggests, what are some common examples (other than **九** ) where
multiple readings apply for the sake of nuances? For instance, for **四分** ,
what are the possible readings? `よぶ, よんぶ, and/or しぶ?` In addition, how does
one read `何分, 一分, 三分, 八分, 十分, 百分`, and so on?

* * *

Unfortunately, that is not all.

First of all, as far as I know, **分** should be read as **ぶん** for fractions,
such as **三分{さんぶん}の一{いち}**. The same goes for portions, such as **千人分の生ビール** ,
or **三十年分のビール**.

Next, I looked up **分** again in a dictionary, and for this specific
pronunciation, **ぶ** , _研究社_ listed only one English translation,
**"percent."** The following are all the sample sentences provided:

>   1. 銀行は 4 *分の利子で金を貸してくれた。 The bank lent me the money at 4 percent interest.
>
>   2. 日本チームに*分がある勝ちそうだ。 The Japanese team is likely to win.
>
>   3. 今回は我々のほうが*分がいい。 We have an advantage this time.
>
>   4. その仕事は 9 *分どおり済んだ。 The work is 90 percent done.
>
>

For 2. & 3., I think **ぶ** is the only possible reading, since only under
**ぶ** is this meaning listed. In _goo辞書_ , 1st entry under **分（ぶ）** :

> どちらに傾くかの度合い。自分のほうに有利になる度合い。

**Question #2.**  
For 1. & 4., can you read it as **ぶん** as well? Moreover, shouldn't it be **9
percent** in 4., or **九割**?

* * *

Again, under **割（り）（わり）** , _goo辞書_ has this definition：

>   2. 歩合の単位。1割は10分の1。
>

And for **分（ぶ）** :

>   5. 全体を10等分したもの。10分の1相当の量。
>
>   6. 単位の名。㋐割合・利率で、1割の10分の1。全体の100分の1。
>
>

I guess one does not simply consult a dictionary, and go "Eureka!"

**Question 3.**  
How does one decide, then, when **（一）分** means **one-tenth** , but not **one-
hundredth**? Moreover, how does one read it? **ぶ** , or **ぶん**?

長文ですみません… いつも迷惑をかけてばかりんですが…どうぞよろしくお願いいたします！




**A1:** When 分 means 10%, 一分 ～ 九分 is usually read like いちぶ, にぶ, さんぶ, よんぶ, ごぶ,
ろくぶ, ななぶ/しちぶ, はちぶ, きゅうぶ/くぶ. But 九分九厘 is an idiom that is always pronounced
くぶくりん. 九割九分 is usually きゅうわりきゅうぶ, but くわりくぶ may not be wrong. 何分 is なんぶ.

**A2:** These are read as 4分【ぶ】の利子, 分【ぶ】がある, 分【ぶ】がいい, 9分【ぶ】どおり. No exceptions.
その仕事は9分どおり済んだ and その仕事は9割済んだ effectively mean the same thing, 90%. See below.

**A3:** 分 read as ぶ **essentially means 10%** , not 1%. However, 分 **appears
to mean 1%** if it follows 割, which is another term meaning 10%.

割 means "10% of the entire fraction". 分 on its own works like 割, but 分 also
works somewhat like the SI prefix _deci-_ ; it's used in combination with
another unit and refers to one tenth of it. For example, 一寸五分 (いっすんごぶ) means
1.5 [sun](https://en.wikipedia.org/wiki/Cun_\(unit\)) (≒4.5 cm), and 37度5分
(さんじゅうななどごぶ) means 37.5 ℃. Likewise, when 割 and 分 are used together, 2割5分
means "2.5割", which is 25%. This explains why both 九割九分 and 九分九厘 mean 99%.

That being said, for historical reasons, 分 means 1% even without 割 in
financial contexts and baseball contexts. 4分 (よんぶ) automatically means 4% when
you are talking about interest rates and batting averages. Outside of these
types of situations, you can assume that 分 read as ぶ means 10% (cf 四分咲き → 40%,
七分袖 → 70%, 五分五分 → fifty-fifty).

[![enter image description
here](https://i.stack.imgur.com/CuGzQ.png)](https://i.stack.imgur.com/CuGzQ.png)

You seem to correctly understand how to read 3分【ぶん】の1, 30年【ねん】分【ぶん】のビール,
2時30分【ぷん】, and so on, so I won't go into detail about them.




**A1:** When 分 means 10%, 一分 ～ 九分 is usually read like いちぶ, にぶ, さんぶ, よんぶ, ごぶ,
ろくぶ, ななぶ/しちぶ, はちぶ, きゅうぶ/くぶ. But 九分九厘 is an idiom that is always pronounced
くぶくりん. 九割九分 is usually きゅうわりきゅうぶ, but くわりくぶ may not be wrong. 何分 is なんぶ.

**A2:** These are read as 4分【ぶ】の利子, 分【ぶ】がある, 分【ぶ】がいい, 9分【ぶ】どおり. No exceptions.
その仕事は9分どおり済んだ and その仕事は9割済んだ effectively mean the same thing, 90%. See below.

**A3:** 分 read as ぶ **essentially means 10%** , not 1%. However, 分 **appears
to mean 1%** if it follows 割, which is another term meaning 10%.

割 means "10% of the entire fraction". 分 on its own works like 割, but 分 also
works somewhat like the SI prefix _deci-_ ; it's used in combination with
another unit and refers to one tenth of it. For example, 一寸五分 (いっすんごぶ) means
1.5 [sun](https://en.wikipedia.org/wiki/Cun_\(unit\)) (≒4.5 cm), and 37度5分
(さんじゅうななどごぶ) means 37.5 ℃. Likewise, when 割 and 分 are used together, 2割5分
means "2.5割", which is 25%. This explains why both 九割九分 and 九分九厘 mean 99%.

That being said, for historical reasons, 分 means 1% even without 割 in
financial contexts and baseball contexts. 4分 (よんぶ) automatically means 4% when
you are talking about interest rates and batting averages. Outside of these
types of situations, you can assume that 分 read as ぶ means 10% (cf 四分咲き → 40%,
七分袖 → 70%, 五分五分 → fifty-fifty).

[![enter image description
here](https://i.stack.imgur.com/CuGzQ.png)](https://i.stack.imgur.com/CuGzQ.png)

You seem to correctly understand how to read 3分【ぶん】の1, 30年【ねん】分【ぶん】のビール,
2時30分【ぷん】, and so on, so I won't go into detail about them.

