Suppose that the following example:


In these cases that take a date as the predicate, I usually see 为 instead of 是. Both mean "is" and I already learned 为 is more formal than 是.

However, I feel I have only seen 为 if it takes a date on its predicate. So I wonder whether it must be 为 if you take a date as the predicate or it is just a coincidence.

Also, is there any case that 为 must be used in the usage of “is” or “be”, not just because of "formal"?

  • 1
    '为' in "印刷术、火药、指南针、‌​纸统称~四大发明" follows the verb 称(be called). It is not equivalent to 'is' but 'as'
    – Tang Ho
    Jan 26 '18 at 17:18
  • "are called" ("called as" ?), "call sth sth" example of "Double Accusative Construction", which may correspond "V+N+as+N" for some other verbs, "denominate sth. as sth (?)", in the present it might be argued that 为 in E corresponds to "nothing"
    – user6065
    Jan 26 '18 at 21:21


[3] [v] be; is; be equivalent to

为 has many different meanings, "is" (是) is just one of them.

You can replace '为' with '是' if you are using it as 'is' in the context.

  • 报名截止日期为2月17日。(literary)

  • 报名截止日期是2月17日。(colloquial)

Also, is there any case that 为 must be used, not just because of "formal"?

You must use '为' instead of '是' when '为' doesn't mean 'is' in the context.

For example:

  • '为' in "印刷术、火药、指南针、‌​纸统称为四大发明" follows the verb 称(be called). '为' here is not equivalent to 'is' but 'as'.

  • You cannot say "印刷术、火药、指南针、‌​纸[统称]古代中国四大发明"

  • But you can say "印刷术、火药、指南针、‌​纸, []古代中国四大发明" or "印刷术、火药、指南针、‌​纸[]古代中国四大发明"

because [印刷术、火药、指南针、‌​纸] [is] [古代中国四大发明]


If it is a written announcement, no matter what the predicate is, you should use 为.

Posting '报名截止日期[是]2月17日' or '报名费用[是]成人二十元,老人和儿童半价' is considered bad vocabulary choice (using colloquial term when it should be literary)

If it is an oral conversation, no matter what the predicate is, you should use 是

Telling someone '报名截止日期[为]2月17日' or '报名费用[为]成人二十元,老人和儿童半价' is also considered bad vocabulary choice (using literary term when it should be colloquial)

  • Thanks but I meant 为 in the use of “is”. I know it is also used as “as” but it is not in the scope of my question. I updated it to make it clearer.
    – Blaszard
    Jan 26 '18 at 20:26
  • If the meaning is 'is', then using '为' is more literary and using '是' is more colloquial. As I stated in my answer. They are interchangeable , as the two example sentences showed.
    – Tang Ho
    Jan 26 '18 at 22:04
  • Yes I know it is. But my question is about the date (or number I think as well). Is there any difference if the predicate is a date or not, regarding which verb to use?
    – Blaszard
    Jan 27 '18 at 11:27
  • See my edition at the bottom.
    – Tang Ho
    Jan 27 '18 at 13:21
  • 1
    It is OK. to use 是 in literary form, for example, in written dialogue. But in an announcement, it is not a good choice of vocabulary; It is also OK. to use 为 in oral conversation if you are treating it like a quote or when you read from a written text.
    – Tang Ho
    Jan 27 '18 at 14:02

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