<p>As far as I know, the main difference lies in how formal they are. 是 is mostly used in colloquial Chinese, whereas 為/为 is much more formal, often used in constructions like 以...為... or just as a single character （1999年国民经济增长预期目标为7%）. </p>

<p>Of course, it should be noted that 為/为 can mean other things than 是, but since you compare it with 是, I'm guessing that's not the problem here. 為/为 is read second tone when it means 是 (that's neither the only meaning of a second tone wei2 nor the only reading of the character, though). If you're not sure about the different kinds of 為/为, perhaps this entry over at Zdic will be useful: <a href="http://www.zdic.net/zd/zi/ZdicE4ZdicB8ZdicBA.htm" rel="nofollow">http://www.zdic.net/zd/zi/ZdicE4ZdicB8ZdicBA.htm</a>. </p>

CC BY-SA 3.0
2013-04-03T00:32:40.683Z
2013-04-03T00:32:40.683Z
Olle Linge
<p>Both words have very broad usages (literal, rhetorical, metaphorical, etc.) and subtleties that must be analyzed within context. Generally speaking, 是 vs. 为 is similar to 'being' vs. '(serving) as', that is, 是 defines the subject while 为 scopes the connotation and/or extension of it. </p>

CC BY-SA 3.0
2013-04-03T01:05:00.057Z
2013-04-03T01:05:00.057Z
NS.X.
<p>为 has a lot meanings, and so does 是. A common meaning between 为 and 是 is "to be" or other variations of "to be", like "being". 为 is used more for its other meanings than "to be", while 是 is used more for "to be" than its other meanings. When meaning "to be", in some cases, 为 and 是 are interchangeable. For example: </p>

<blockquote>
  <ul>
  <li>我们今年的工作目标 <strong>为</strong> ... </li>
  <li>我们今年的工作目标 <strong>是</strong> ...</li>
  </ul>
</blockquote>

<p>But there are some cases where 是 <strong>cannot</strong> be replaced by 为, for example: </p>

<blockquote>
  <p><strong>Yes</strong>: 我 <strong>是</strong> 一名学生.<br>
  <strong>No</strong>: 我 <strong>为</strong> 一名学生(X). </p>
</blockquote>

<p>为 has another meaning very close to "to be", which is <em>"regard ... as ... "</em> in the pattern of 以...为..., for example </p>

<blockquote>
  <p><strong>以</strong> 厂 <strong>为</strong> 家, <strong>以</strong> 人 <strong>为</strong> 本, 民 <strong>以</strong> 食 <strong>为</strong> 天, <strong>以</strong> 救国救民 <strong>为</strong> 己任, etc. </p>
</blockquote>

<p>In this case, 为 <strong>cannot</strong> be replaced with 是. By the way, 为 and 是 can even be used together, like 自以为是. But here 为 means "believe", and 是 means "right", or "correct". 自以为是 means "consider oneself always right". 自以为是 is a derogatory term, used to show dislike, disagreement or disapproval.</p>

<p>Another example: </p>

<blockquote>
  <p>是为序。</p>
</blockquote>

<p>Here 是 means "this", 为 means "is", 序 is "preface", so the whole sentence means "this is the preface". It is sometimes used to end a preface.</p>

<p>One more example: </p>

<blockquote>
  <p>何以为是，何以为非？无以为是，无以为非。 </p>
</blockquote>

<p>Here both 是 mean "true" or "truth", both 非 mean "false" or "falsehood". All the 4 为 mean "to be". </p>

<p>According to above-mentioned samples, 为 means that it is NOT xxx but very like xxx. In Chinese words, (可能它一定不是xx，但也可能它现在不是xx，将来可能是, 但)把它当作是xx。</p>

<p>Example: 以厂为家，厂 is not home，but someone treats it as home。 </p>

<blockquote>
  <p>今年的目标为xx，i.e. 我们把xx当作今年的目标。 </p>
</blockquote>

<p>为 implies that we assign a role to a thing actively/explicitly, but 是 implies that a thing does natively have the role.</p>

CC BY-SA 3.0
2013-04-04T08:48:39.330Z
This answer has a lot of information in it. But I still don't understand what cases they are interchangable and what cases they aren't. NS.X.'s answer is more in line with my previous understanding. Would it be possible to get some more robust examples?
tao
CC BY-SA 3.0
2013-04-04T16:52:26.910Z
@tao: Unfortunately, language is not science. It is hard to make rules/usages in language and it is worthy to note that even there are rules out there, sometimes rules can also hinder us. As long as there are rules, there are always exceptions, so why bother spending time on trying to remember all the rules and exceptions? I belive learning thru examples is better than learning by rules. All native spearkers learn their mother languages thru examples, not by rules. What makes it even worse for Chinese is that Chinese language's grammar/usages are very weak.
孤影萍踪
CC BY-SA 3.0
2013-04-05T06:36:47.123Z
The pithy example sometimes given is [穿 vs 戴](http://chinesehacks.com/vocabulary/which-wear-and-when-to-use-it-in-chinese/), for which there is no exception-less rule on when to use each.
congusbongus
CC BY-SA 4.0
2020-01-18T10:12:54.917Z
This is an exceptionally good answer.
Becky 李蓓
CC BY-SA 3.0
2013-04-03T19:41:12.387Z
2013-04-11T22:15:45.217Z
2013-04-11T22:15:45.217Z
孤影萍踪
<p>It seems like both 为 and 是 mean "to be". In which cases is one used but not the other? Is it something like the difference between "estar" and "ser" in Spanish and Portuguese? (In the sense that one is constant in time while the other is transient). Thanks.</p>

CC BY-SA 3.0
2013-04-03T04:59:47.640Z
Maybe: 爲 is dynamic, 是 is static? 爲 and 是 vs 爲 and 也 as in Classical Chinese.
Mike Manilone
<mandarin><meaning><usage><synonyms><difference>
What's the main difference between 为 and 是?
# What's the main difference between 为 and 是?

(Asked by: username_0 on 2013-04-02)

It seems like both 为 and 是 mean "to be". In which cases is one used but not the other? Is it something like the difference between "estar" and "ser" in Spanish and Portuguese? (In the sense that one is constant in time while the other is transient). Thanks.

**Tags:** mandarin, meaning, usage, synonyms, difference
> **Comments:**
> **username_1**: Maybe: 爲 is dynamic, 是 is static? 爲 and 是 vs 爲 and 也 as in Classical Chinese.  

---

## 3 answers

### Answer by username_4 on 2013-04-03. Score: 10 | Accepted answer

为 has a lot meanings, and so does 是. A common meaning between 为 and 是 is "to be" or other variations of "to be", like "being". 为 is used more for its other meanings than "to be", while 是 is used more for "to be" than its other meanings. When meaning "to be", in some cases, 为 and 是 are interchangeable. For example:

> * 我们今年的工作目标 **为** ...
> * 我们今年的工作目标 **是** ...

But there are some cases where 是 **cannot** be replaced by 为, for example:

> **Yes**: 我 **是** 一名学生.  
> **No**: 我 **为** 一名学生(X).

为 has another meaning very close to "to be", which is *"regard ... as ... "* in the pattern of 以...为..., for example

> **以** 厂 **为** 家, **以** 人 **为** 本, 民 **以** 食 **为** 天, **以** 救国救民 **为** 己任, etc.

In this case, 为 **cannot** be replaced with 是. By the way, 为 and 是 can even be used together, like 自以为是. But here 为 means "believe", and 是 means "right", or "correct". 自以为是 means "consider oneself always right". 自以为是 is a derogatory term, used to show dislike, disagreement or disapproval.

Another example:

> 是为序。

Here 是 means "this", 为 means "is", 序 is "preface", so the whole sentence means "this is the preface". It is sometimes used to end a preface.

One more example:

> 何以为是，何以为非？无以为是，无以为非。

Here both 是 mean "true" or "truth", both 非 mean "false" or "falsehood". All the 4 为 mean "to be".

According to above-mentioned samples, 为 means that it is NOT xxx but very like xxx. In Chinese words, (可能它一定不是xx，但也可能它现在不是xx，将来可能是, 但)把它当作是xx。

Example: 以厂为家，厂 is not home，but someone treats it as home。

> 今年的目标为xx，i.e. 我们把xx当作今年的目标。

为 implies that we assign a role to a thing actively/explicitly, but 是 implies that a thing does natively have the role.

> **Comments:**
> **username_5**: This answer has a lot of information in it. But I still don't understand what cases they are interchangable and what cases they aren't. NS.X.'s answer is more in line with my previous understanding. Would it be possible to get some more robust examples?  
> **username_4**: @tao: Unfortunately, language is not science. It is hard to make rules/usages in language and it is worthy to note that even there are rules out there, sometimes rules can also hinder us. As long as there are rules, there are always exceptions, so why bother spending time on trying to remember all the rules and exceptions? I belive learning thru examples is better than learning by rules. All native spearkers learn their mother languages thru examples, not by rules. What makes it even worse for Chinese is that Chinese language's grammar/usages are very weak.  
> **username_6**: The pithy example sometimes given is [穿 vs 戴](http://chinesehacks.com/vocabulary/which-wear-and-when-to-use-it-in-chinese/), for which there is no exception-less rule on when to use each.  
> **username_7**: This is an exceptionally good answer.  

---

### Answer by username_2 on 2013-04-03. Score: 2

As far as I know, the main difference lies in how formal they are. 是 is mostly used in colloquial Chinese, whereas 為/为 is much more formal, often used in constructions like 以...為... or just as a single character （1999年国民经济增长预期目标为7%）.

Of course, it should be noted that 為/为 can mean other things than 是, but since you compare it with 是, I'm guessing that's not the problem here. 為/为 is read second tone when it means 是 (that's neither the only meaning of a second tone wei2 nor the only reading of the character, though). If you're not sure about the different kinds of 為/为, perhaps this entry over at Zdic will be useful: <http://www.zdic.net/zd/zi/ZdicE4ZdicB8ZdicBA.htm>.


---

### Answer by username_3 on 2013-04-03. Score: 0

Both words have very broad usages (literal, rhetorical, metaphorical, etc.) and subtleties that must be analyzed within context. Generally speaking, 是 vs. 为 is similar to 'being' vs. '(serving) as', that is, 是 defines the subject while 为 scopes the connotation and/or extension of it.


---

