<p>YI2 GE4 or yi2 ge5 are both correct, and it depends on where you using them.
When we use 一 and a quantifier together, we always proniunce 一 as Yi2, and there is no specific reason.</p>

CC BY-SA 3.0
2012-09-12T18:27:50.740Z
Consider your answer more carefully: In `一本书`, it's pronounced yi4 (**not** yi2). The reason for the tone change isn't because there's a classifier. It's because of the tone of the following syllable.
Stumpy Joe Pete
CC BY-SA 3.0
2012-09-12T16:33:47.610Z
2012-09-12T16:33:47.610Z
Chenhao
<p>一 is pronounced in the first tone when it stands alone.
It is pronounced in the fourth tone when it precedes a first, second, or third tone. However, it is pronounced in the second tone when it precedes a fourth tone. 不 is a bit similar: It is also pronounced in the fourth tone when it precedes a first, second, or third tone. However, it is pronounced in the second tone when it precedes a fourth tone.</p>

<p>Some examples (from: <a href="http://web.mit.edu/jinzhang/www/pinyin/tones/index.html#1bu">http://web.mit.edu/jinzhang/www/pinyin/tones/index.html#1bu</a> but I used simplified characters instead and corrected a tone which is incorrect on that website)</p>

<ul>
<li>一万 (yíwàn)
(ten thousand)  </li>
<li>一块 (yíkuài)
(one dollar)</li>
<li>一半 (yíbàn)
( a half)</li>
<li>不贵 (búguì)
(not expensive) </li>
<li>不对 (búduì)
(not correct)</li>
<li><p>不慢 (búmàn)
(not slow)</p></li>
<li><p>一天 (yìtiān)
(a day) </p></li>
<li>一生 (yìshēng)
(one's whole life)</li>
<li>不多 (bùduō)
(not many/much)</li>
<li><p>不吃 (bùchī)
(not eat)</p></li>
<li><p>一年 (yìnián)
(a year)    </p></li>
<li>一群 (yìqún)
(a group of)</li>
<li>不难 (bùnán)
(not difficult)</li>
<li><p>不忙 (bùmáng)
(not busy)</p></li>
<li><p>一晚 (yìwǎn) 
(one night) </p></li>
<li>一早 (yìzǎo)
(early in the morning)</li>
<li>不晚 (bùwǎn)
(not late)</li>
<li>不早 (bùzǎo)
(not early)</li>
</ul>

<p>Since 个 has a fourth tone, the tone of 一 should become a second tone. Although in practice 个 is most often spoken as a neutral tone, the original tone is used for the <a href="http://en.wikipedia.org/wiki/Tone_sandhi">tone sandhi</a>.</p>

CC BY-SA 3.0
2012-09-02T08:17:29.083Z
If I understand correctly... do you mean that `是不是` should be indeed pronounced shi4 bu2 shi4 instead of shi4 bu4 shi4 ?
Stephane Rolland
CC BY-SA 3.0
2012-09-02T16:45:15.803Z
Correct. shi4 bu2 shi4.
Stumpy Joe Pete
CC BY-SA 3.0
2012-09-02T17:38:58.167Z
Yes, it is shi4 bu2 shi4, but when speaking most people won't pronounce the second tone of bu in shi4 bu2 shi4, so they will say shi4 bu shi4
BertR
CC BY-SA 3.0
2013-02-20T03:03:13.067Z
perhaps you could mention something about the "shortening" of the 一 in 一个. In normally paced speech  it becomes so short that the tone is irrelevant. Like English "this is for you" being  pronounced "this is f'you", 一个人 sounds to me much more like "y'ge rén" (yes I am aware this is not valid pinyin :)
jsj
CC BY-SA 3.0
2012-09-01T12:21:19.273Z
2012-09-01T12:21:19.273Z
BertR
<p>When I first learnt the numbers, I learnt <code>一</code> with the first tone <code>yi1</code>.</p>

<p>But now, during a <a href="http://www.memrise.com">Memrise</a> lesson, they teach me that <code>一个</code> should be pronounced <code>yi2 ge4</code> or <code>yi2 ge5</code>.</p>

<p>Is this correct and, if so, is there a reason for that pronunciation?</p>

CC BY-SA 3.0
2012-09-07T05:33:38.580Z
Chinese don't have 5 pronunciation.
Lix
CC BY-SA 3.0
2012-09-07T05:36:52.943Z
@Lix - Welcome to Chinese.SE! I have changed your answer to a comment. For new users you need certain privileges to be able to do certain actions such as commenting. If you need more reputation to do an action please respect the site and work towards gaining more reputation so you can use those features.
going
CC BY-SA 3.0
2012-09-07T06:09:35.060Z
@Lix Indeed there is 5. 1: tone up to tone up, 2: tone down to tone up, 3: tone down to even more down then to tone up, 4: tone up to tone down, 5: short neutral tone. cf: ma, ba, ne, ge, zi, er... according the notation, they are written 0, 5, or just nothing.
Stephane Rolland
<pronunciation><tones><sandhi>
Pronunciation of 一 in 一个
# Pronunciation of 一 in 一个

(Asked by: username_0 on 2012-09-01)

When I first learnt the numbers, I learnt `一` with the first tone `yi1`.

But now, during a [Memrise](http://www.memrise.com) lesson, they teach me that `一个` should be pronounced `yi2 ge4` or `yi2 ge5`.

Is this correct and, if so, is there a reason for that pronunciation?

**Tags:** pronunciation, tones, sandhi

> **Comments:**
> **username_1**: Chinese don't have 5 pronunciation.  
> **username_2**: @username_1 - Welcome to Chinese.SE! I have changed your answer to a comment. For new users you need certain privileges to be able to do certain actions such as commenting. If you need more reputation to do an action please respect the site and work towards gaining more reputation so you can use those features.  
> **username_0**: @username_1 Indeed there is 5. 1: tone up to tone up, 2: tone down to tone up, 3: tone down to even more down then to tone up, 4: tone up to tone down, 5: short neutral tone. cf: ma, ba, ne, ge, zi, er... according the notation, they are written 0, 5, or just nothing.  

---

## 2 answers

### Answer by username_5 on 2012-09-01. Score: 12 | Accepted answer

一 is pronounced in the first tone when it stands alone.
It is pronounced in the fourth tone when it precedes a first, second, or third tone. However, it is pronounced in the second tone when it precedes a fourth tone. 不 is a bit similar: It is also pronounced in the fourth tone when it precedes a first, second, or third tone. However, it is pronounced in the second tone when it precedes a fourth tone.

Some examples (from: <http://web.mit.edu/jinzhang/www/pinyin/tones/index.html#1bu> but I used simplified characters instead and corrected a tone which is incorrect on that website)

* 一万 (yíwàn)
  (ten thousand)
* 一块 (yíkuài)
  (one dollar)
* 一半 (yíbàn)
  ( a half)
* 不贵 (búguì)
  (not expensive)
* 不对 (búduì)
  (not correct)
* 不慢 (búmàn)
  (not slow)
* 一天 (yìtiān)
  (a day)
* 一生 (yìshēng)
  (one's whole life)
* 不多 (bùduō)
  (not many/much)
* 不吃 (bùchī)
  (not eat)
* 一年 (yìnián)
  (a year)
* 一群 (yìqún)
  (a group of)
* 不难 (bùnán)
  (not difficult)
* 不忙 (bùmáng)
  (not busy)
* 一晚 (yìwǎn)
  (one night)
* 一早 (yìzǎo)
  (early in the morning)
* 不晚 (bùwǎn)
  (not late)
* 不早 (bùzǎo)
  (not early)

Since 个 has a fourth tone, the tone of 一 should become a second tone. Although in practice 个 is most often spoken as a neutral tone, the original tone is used for the [tone sandhi](http://en.wikipedia.org/wiki/Tone_sandhi).

> **Comments:**
> **username_0**: If I understand correctly... do you mean that `是不是` should be indeed pronounced shi4 bu2 shi4 instead of shi4 bu4 shi4 ?  
> **username_4**: Correct. shi4 bu2 shi4.  
> **username_5**: Yes, it is shi4 bu2 shi4, but when speaking most people won't pronounce the second tone of bu in shi4 bu2 shi4, so they will say shi4 bu shi4  
> **username_6**: perhaps you could mention something about the "shortening" of the 一 in 一个. In normally paced speech  it becomes so short that the tone is irrelevant. Like English "this is for you" being  pronounced "this is f'you", 一个人 sounds to me much more like "y'ge rén" (yes I am aware this is not valid pinyin :)  

---

### Answer by username_3 on 2012-09-12. Score: 1

YI2 GE4 or yi2 ge5 are both correct, and it depends on where you using them.
When we use 一 and a quantifier together, we always proniunce 一 as Yi2, and there is no specific reason.

> **Comments:**
> **username_4**: Consider your answer more carefully: In `一本书`, it's pronounced yi4 (**not** yi2). The reason for the tone change isn't because there's a classifier. It's because of the tone of the following syllable.  

---

