While I was studying Chinese, I came across three sentences. I couldn't find out when 是 should be used. The sentences were as follows:

  1. 明天星期六。
  2. 5 月25 号是星期天。
  3. 今年是2021年。 I couldn't know why 是 was not used in the first sentence?

5 Answers 5



This structure is called "Nominal Predicate Sentence" (名词谓语句). In this structure a nominal construction or compound is used as predicate. Normally, it is not used a simple noun. For example, we'd not say (sentences marked with * are wrong):

  • *我刘波。
  • *这画报。

(All examples are taken from 《现代汉语八百词》,吕叔湘主编).

Nominal constructions or compounds are generally used as nominal predicates. For example:

  • 我十九岁。
  • 你哪儿人?

This type of sentence is mainly used to show time, age, one's birthplace, one's appearance, etc.

In the affirmative sentence, 是 is not used, but it must be used in the negative, as in:

  • 明天不是星期六。

Anyway, 是 can be added to most nominal predicate sentences, as in:

  • 哪儿人?

And it is not forbidden to add it even in:

  • 十九岁。
  • 明天星期六。

unfortunately some of the Chinese sentences don't need verb. In general when you make sentence with adjective and predicate; adjective plays as a verb. 我很好。 他最近有点儿不高兴。 北京冬天的天气非常冷。 some specific sentences don't need a verb, like date related sentences. the other words will play as a verb. for example 明天星期六 you will get the meaning without 是. 是 is usually used as glue between two nouns.


The difference between 明天是星期六 and 明天星期六:

明天是星期六 (tomorrow is Saturday) is a complete sentence with 是 as the verb

明天星期六 (tomorrow Saturday) has no verb. It is a phrase made up of a noun and its relative noun. The noun is 明天, and 星期六 is the relative noun that provides additional information on it.


我明天不用上學 is a complete sentence

明天(星期六)不用上學 - the relative noun 星期六 provides additional information on the noun 明天

明天(七月十四號)(星期四)(校慶)不用上學 - all three nouns, 七月十四號, 星期四, and 校慶 describe 明天. They are the same day

  • 明天不用上學

  • 明天七月十四號不用上學

  • 明天七月十四號星期四不用上學

  • 明天七月十四號星期四校慶不用上學

Each relative noun adds additional information to 明天

Similar example:

我們在香港工作 (we work in Hong Kong)

我們兄弟倆在香港工作 (we two brothers work in Hong Kong)

'我們是兄弟倆' would be a complete sentence, and 在香港工作 has to be a separate sentence - e.g. "我們是兄弟倆,都在香港工作"


The first sentence can be considered as an omission of verb 是.

In some grammar books, they take it as 名词性谓语句(noun as predicate). E. g. 今天星期四. 明天晴天。这张桌子四条腿。

Note that Chinese sentences don't have to have a verb as predicate.


Without "是", the first can't be counted as a stand-along (complete) sentence.

It can be used in a sentence as emphatic phrases in a brief conversation - 明天, 星期六, 車站前碰面。

Or indicating the date in a logical manner - 今天星期五, 明天星期六, 她後天應該會抵達。(She, the guest, has arranged to arrive on Sunday, the speaker is counting the dates to ensure he hasn't missed the arrival of the guest.)

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