<p>Interesting question. Is there a preference when it comes to using 天 for 日?</p>

<p>In my opinion, there are no such a strict rules when it comes 天vs日.(I was born and raised in southern China, lived in the North for several years. I speak Cantonese, Mandarin, Hakka)</p>

<p>Basically, 周天and周日, 星期日and星期天,明日and明天, 改日and改天 are all equivalent. But why people prefer one to another?</p>

<p>There're some reasons: </p>

<ol>
<li><p>In some south-western dialects, 日and一 have similar pronunciation. So people prefer use 周天than周日。</p></li>
<li><p>Speaking in rhyme. 天tian1, 日ri4. So in some cases, it sounds weird to use天, but in another case, it sounds weird to use 日。That's depends.</p></li>
</ol>

CC BY-SA 3.0
2017-05-14T00:13:51.680Z
2017-05-14T00:13:51.680Z
Kevman
<p>we use 天 in oral Chinese, but 日 in writing Chinese, this is related to tone of  characters, pronouncing fourth tone (4 声，入声) takes more efforts, so that we pronounce other characters with same meanings. i.e. 两个 other than 二个. Pronouncing characters with 3rd tone lengthen time of pronunciation to decrease rhythm, so that we save some efforts when we need speak loudly or in a long speech &amp; lecture, sometimes we also avoid pronouncing multiple adjacent 3rd-tone characters, i.e. pronouncing 处理 (chu2 li3) other than original tone chu3 li3 (which is hard to pronounce loudly/quickly), avoid opening your mouth wide frequently or persistently, we rather pronounce with with alternant open/close mouth combinations.</p>

CC BY-SA 3.0
2017-05-22T05:08:27.757Z
2017-05-22T05:30:00.820Z
2017-05-22T05:30:00.820Z
Daniel Yang
<p>In my opinion，天 is more often use on 白话文 and normal conversation.</p>

<p>Because 天 is more natural and easy to pronounce than 日 when talking.</p>

<p>日 is more often use on 文言文。</p>

<p>For example in 佛说阿弥陀经,</p>

<blockquote>
  <p>舍利弗，若有善男子、善女人，闻说阿弥陀佛，执持名号，<strong>若一日、若二日、若三日、若四日、若五日、若六日、若七日</strong>，一心不乱。</p>
</blockquote>

CC BY-SA 3.0
2017-05-03T00:02:33.467Z
2017-05-03T00:02:33.467Z
Chek Wei Tan
<p>happy to help you learn chinese,im chinese if i express wrong in english grammar hope you can forgive me.ok,lets begin,in china,we use 日 in this condition:今天是5月14日 or 5月14号，as you see,usually use 日 to express date,use 天 to count,like ‘一年有365天’,‘第几个一百天’
and i want to make a friend to communicate,just help each other learn languages,if you major in computer science or software,it couldn't be better!</p>

CC BY-SA 3.0
2017-05-14T15:10:28.680Z
2017-05-14T15:10:28.680Z
jayce_hu
<p>In Hong Kong or GuangDong, Cantonese still use 日 for 'day.' For example: ' 几日返来啊？' For Mandarin speakers, 天 tian is easier and more natural  to pronounce than 日 ri. </p>

<p>Also, <strong>日</strong> sounds like <strong>入</strong> (enter). Which is the <strong>F word</strong> in Chinese.</p>

<p>Last but not least, it's also because of the Japanese invasion of China. Japan in Chinese is 日. Since general Chinese didn't like Japan, they unconsciously avoided using 日.</p>

CC BY-SA 3.0
2017-05-02T23:31:01.160Z
It is all speculation in Atmega's part. There's no evidence for any of the three reasons he listed.
Tang Ho
CC BY-SA 3.0
2017-05-02T22:48:15.610Z
2017-05-02T23:29:02.860Z
2017-05-02T23:29:02.860Z
Atmega 328
<p>In Classical Chinese, the proper word for counting days is 日. In Southern Chinese languages, 日 is more prevalent in counting days. Why 天 is chosen for counting days in Mandarin instead of 日? </p>

<p><strong>Edit</strong></p>

<p>More, in Mandarin it is quite usual to replace 日 with 天 for some words related to day. For example:</p>

<ul>
<li>星期日 禮拜日 (Sunday) to 星期天 禮拜天</li>
<li>明日 (Tomorrow) to 明天</li>
<li>改日 (another day) to 改天</li>
<li>日日 (Everyday) to 天天</li>
<li>當日 (At that day) to 當天</li>
</ul>

CC BY-SA 3.0
2017-05-03T00:48:34.333Z
It's an interesting topic, but I think you're unlikely to get a satisfying answer. You could ask the same thing about almost any vocab difference. Why 红 and not 赤? 听 instead of 闻? For that matter, I don't think you'd get a satisfying answer as to why particular dialects went one direction or the other on certain vocabulary items (e.g., 知道 vs 晓得, 东西 vs 物事, 今天 vs 今朝).
Stumpy Joe Pete
CC BY-SA 3.0
2017-05-03T08:31:28.123Z
日 is considered 忌讳 (taboo) in some (southern Chinese) dialects because it's 谐音 with 入 (an equivalent of 肏). Words like 向日葵 become 向儿葵. Perhaps this could be a reason.
Mou某
CC BY-SA 3.0
2017-05-13T11:56:17.637Z
I would say that it is just culture.
paper1111
<word-choice><mandarin><usage><etymology>
Why 天 is chosen for counting days instead of 日 in Mandarin?
# Why 天 is chosen for counting days instead of 日 in Mandarin?

(Asked by: username_0 on 2017-05-02)

In Classical Chinese, the proper word for counting days is 日. In Southern Chinese languages, 日 is more prevalent in counting days. Why 天 is chosen for counting days in Mandarin instead of 日?

**Edit**

More, in Mandarin it is quite usual to replace 日 with 天 for some words related to day. For example:

* 星期日 禮拜日 (Sunday) to 星期天 禮拜天
* 明日 (Tomorrow) to 明天
* 改日 (another day) to 改天
* 日日 (Everyday) to 天天
* 當日 (At that day) to 當天

**Tags:** word-choice, mandarin, usage, etymology

> **Comments:**
> **username_1**: It's an interesting topic, but I think you're unlikely to get a satisfying answer. You could ask the same thing about almost any vocab difference. Why 红 and not 赤? 听 instead of 闻? For that matter, I don't think you'd get a satisfying answer as to why particular dialects went one direction or the other on certain vocabulary items (e.g., 知道 vs 晓得, 东西 vs 物事, 今天 vs 今朝).  
> **username_2**: 日 is considered 忌讳 (taboo) in some (southern Chinese) dialects because it's 谐音 with 入 (an equivalent of 肏). Words like 向日葵 become 向儿葵. Perhaps this could be a reason.  
> **username_3**: I would say that it is just culture.  

---

## 5 answers

### Answer by username_4 on 2017-05-14. Score: 2

Interesting question. Is there a preference when it comes to using 天 for 日?

In my opinion, there are no such a strict rules when it comes 天vs日.(I was born and raised in southern China, lived in the North for several years. I speak Cantonese, Mandarin, Hakka)

Basically, 周天and周日, 星期日and星期天,明日and明天, 改日and改天 are all equivalent. But why people prefer one to another?

There're some reasons:

1. In some south-western dialects, 日and一 have similar pronunciation. So people prefer use 周天than周日。
2. Speaking in rhyme. 天tian1, 日ri4. So in some cases, it sounds weird to use天, but in another case, it sounds weird to use 日。That's depends.


---

### Answer by username_5 on 2017-05-22. Score: 0

we use 天 in oral Chinese, but 日 in writing Chinese, this is related to tone of characters, pronouncing fourth tone (4 声，入声) takes more efforts, so that we pronounce other characters with same meanings. i.e. 两个 other than 二个. Pronouncing characters with 3rd tone lengthen time of pronunciation to decrease rhythm, so that we save some efforts when we need speak loudly or in a long speech & lecture, sometimes we also avoid pronouncing multiple adjacent 3rd-tone characters, i.e. pronouncing 处理 (chu2 li3) other than original tone chu3 li3 (which is hard to pronounce loudly/quickly), avoid opening your mouth wide frequently or persistently, we rather pronounce with with alternant open/close mouth combinations.


---

### Answer by username_6 on 2017-05-03. Score: -1

In my opinion，天 is more often use on 白话文 and normal conversation.

Because 天 is more natural and easy to pronounce than 日 when talking.

日 is more often use on 文言文。

For example in 佛说阿弥陀经,

> 舍利弗，若有善男子、善女人，闻说阿弥陀佛，执持名号，**若一日、若二日、若三日、若四日、若五日、若六日、若七日**，一心不乱。


---

### Answer by username_7 on 2017-05-14. Score: -1

happy to help you learn chinese,im chinese if i express wrong in english grammar hope you can forgive me.ok,lets begin,in china,we use 日 in this condition:今天是5月14日 or 5月14号，as you see,usually use 日 to express date,use 天 to count,like ‘一年有365天’,‘第几个一百天’
and i want to make a friend to communicate,just help each other learn languages,if you major in computer science or software,it couldn't be better!


---

### Answer by username_8 on 2017-05-02. Score: -1

In Hong Kong or GuangDong, Cantonese still use 日 for 'day.' For example: ' 几日返来啊？' For Mandarin speakers, 天 tian is easier and more natural to pronounce than 日 ri.

Also, **日** sounds like **入** (enter). Which is the **F word** in Chinese.

Last but not least, it's also because of the Japanese invasion of China. Japan in Chinese is 日. Since general Chinese didn't like Japan, they unconsciously avoided using 日.

> **Comments:**
> **username_9**: It is all speculation in username_8's part. There's no evidence for any of the three reasons he listed.  

---

