I came across the following translated example:


Wǒ yīnɡɡāi shì ɡǎnmào le,ěrduo yě yǒudiǎnr ténɡ,búɡuò méi fāshāo 。

I think I caught a cold, and my ears are a little painful, but I don’t have a fever.

What is 是 doing here? I understand 我 - 应该 - 是 - 感冒了 literally as I - should - (?) - catch a cold now / caught a cold.

Edit: I see some confusion between the answers. I will list the different views to see if we can clarify them:

  • @blackgreen and @AxelTong claim (应该)是 is just connecting the Subject 我 (I) to the Noun 感冒了 (catch a cold). I don't like this view because when connecting noun A to noun B with 是 , we are essentially saying A = B, where both nouns A and B need to be of the same type. But this is not the case with 我 (a person) and 感冒了 (a state of the person).

  • @DanielCheung (and possibly @TangHo) claim 是 is part of the structure "是 + information to emphasize + verb (+ object) + 的", to emphasize information in the past. However, here we have 了 instead of 的.

  • 2
    「我應該感冒了」could mean "I should fall sick now".
    – Flux
    Commented Jul 31, 2020 at 8:53

11 Answers 11


I do not agree that 是 is acting as the copula in the sentence. Because even without 是, the following sentences contain the same meaning and only differ in tone:

  • 我应该感冒了
  • 我应该感冒了

This answer comes after reading 「是」,「的」與動詞名物化 by professor 石定栩 of PolyU in Hong Kong. (The title roughly translate to: 是, 的, and Normalization of Verb)

感冒 should be acting as a verb in the sentence, as 是 can be optionally added to the sentence to add stress to the statement. 我应该感冒了 conveys the meaning of: "I think I am really having a cold."

TL;DR, Professor Shi proposes that "是" used in a sentence like

  • 他這樣做合情合理的。 (What he did was very reasonable) VS
  • 他這樣做合情合理。 (What he did was reasonable)

should be treated as a modal verb, before the main verb of the sentence "合情合理", with "是" treated as a modal verb the same way the 2 other referenced papers have had it analyzed.

By the same argument, I believe we can treat 感冒 as the main verb, and 是 as a modal verb, used to intensify the tone of the sentence.

By removing all descriptive words, the sentence simplifies into: "我感冒了", which still carries the essential meaning.

P.S. I believe some Chinese linguists actually prefer treating 应该 and 是 as just verbs (with 是 pointed out in the paper referenced), which would have changed the sentence analysis. However, for some people, it may be more acceptable to allow for modal verbs in Chinese grammar analysis, with the above argument.

  • So I understand your answer means this 是 is the same from the structure "是+information to emphasize + verb (+ object) + 的" to emphasize details in the past? Even though there is no information to emphasize apart from the verb and no particle 的?
    – Puco4
    Commented Jul 29, 2020 at 15:35
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    @Puco4 Yes, pretty much. The site you referenced put an action (verb or verb phrase) in 是……的, which I would think is used similarly here, where the writer emphasizes that they indeed have a cold. The paper I referenced said often 的 is added to form the structure with the emphasis intention, but I think emphasis is also used here. It is just that 了 in used in place because the incidence has already happened. Commented Jul 29, 2020 at 15:41
  • I find that 了 replaces 的 in the 是…的 structure a bit strange, because the 是…的 structure already expresses details in the past. Do you know any reference for this?
    – Puco4
    Commented Jul 29, 2020 at 15:53
  • @Puco4 I unfortunately do not. It sure is difficult to find linguistic papers online. I just happened to stumble upon the paper I referenced. However, as a native Chinese user, I believe it is still grammatically correct to say 我应该是感冒的了, albeit a bit clumsy. The equivalent can be found quite frequently in Cantonese though. 我應該係(是) 感冒 嘅(的) 啊啦 with 嘅啊 concat.ed into 㗎. Commented Jul 29, 2020 at 16:26

Let's simplify the sentence to make it easier to identify the role of 是

他死了 -- he died

他(是)死了 -- he (indeed) died

我输了 -- I lost

我(是)输了 -- I (indeed) lost


Adding 应该 make it complicated

  • 应该 in 我应该 means "should"

  • 应该 in 我应该是 means "probably be"


应该输了 -- I should lose

应该(是)输了 -- I probably (really) have lost

It is hard to apply English grammar into Chinese grammar word for word. I would treat '是' in this context as an adverb. Similar to '真的' (really) or '確實' (indeed)

It is in the adverb position and it does modify the verb

  • 2
    I change my mind, just simply treat 是 as an adverb, similar to 真的 (really) or 確實 (indeed)
    – Tang Ho
    Commented Jul 29, 2020 at 17:41
  • 应该 often has an additional meaning in C-E dictionaries of "must" but it's in the sense of "I must be sick" not "you must pay your taxes". This is what you're describing as "probably be" Commented Jul 30, 2020 at 20:55

是 is the copula in Mandarin. It conveys the meaning of the verb “to be”, but is not conjugated, since Mandarin is an analytic language and makes use of marker words to express ideas like grammatical tenses.

A 是 B means A is B, where B is something which describes A. 是 also “affirms” the asserted relationship between A and B.


English: [I]-[should]-[to be]-[catch a cold]-[already]

Essentially, 是 associates 我 (the subject) with 感冒 (the action in the sentence). 了 is used to show that the cold has been caught by “me”, and is a marker of completion.

  • +1, I think this answer is spot on.
    – dan
    Commented Jul 29, 2020 at 23:37

应该是 here denotes the sense of infer; conjecture; guess; reckoning:. That's why it has been translated as "I think I caught a cold".

是 itself denotes this sense:

1  联系两种事物。


人家是丰年,我们是歉年 /刘老师是近视眼。

Basically, 是 links to things. The latter explains or describes the former. In your case, 感冒了(got cold) explains or describes that 我 is in what state. Other examples: 我应该是A组的。 我是上海的。where A组的 and 上海的 describe 我.

This pair might help you better: 他是上海的(he is shanghainese) VS 他应该是上海的(he should be shanghainese).

  • Could you provide some reference for this meaning? I also consulted now in Dejin Li, Meizhen Cheng. A Practical Chinese Grammar for Foreigners and they just state four meanings for 是: to express judgement (I think they correspond to the special affirmative sentences from my answer), to express existence (the presentative sentences), to denote classification and to denote equality (the simple copula sentences).
    – Puco4
    Commented Jul 31, 2020 at 10:43
  • @Puco4 ok, the one I quoted is from the dictionary on my cellphone. I'll try to find an online dictionary for this later.
    – dan
    Commented Jul 31, 2020 at 11:00

Some one: 你今天怎么了? Me sniffling: 我可能感冒了。


Some one: 你是不是感冒了? Me: 我应该感冒了。

Add "是" when someone has referred to a specific state (catch a cold). You can also add "是" to emphasize the correct state if the answer is no.


Some one: 你弟弟今天是不是发烧了? Me: 不,但他应该感冒了。

Note: it seems unnatural to me if the "是" in "我应该是感冒了" is taken out, i.e.

Some one: 你今天怎么了? Me sniffling: 我应该感冒了。

"我应该感冒了" sounds like "I should be catching a cold", which is totally nonsense (think of "I should be doing my home work" as "我应该写作业了", where "应该" is followed by verbs).

Conversely, "我应该是感冒了" should be translated as "I probably catch a cold". In this case, "应该是" is followed by a state, for example "我的车应该是坏了" as "my car is probably broken". In addition, "应该是" can also be followed by numeral+noun to imply one's job etc., for example "他应该是一个老师" as "he is probably a teacher".

  • "他应该是一个老师" as "he is probably a teacher"", I disagree. 他应该是一个老师 is definitely "He should be a teacher."
    – dan
    Commented Jul 30, 2020 at 22:58
  • "he is probably a teacher" in Chinese should be 他可能是老师. We would be more certain that he is a teacher when we say 他应该是一个老师.
    – dan
    Commented Jul 30, 2020 at 23:25
  • @dan I think in Chinese both "可能" and "应该" can be used for speculation, though they have subtle differences--different grammar, and different translation. "Jack怎么没来上班"-->"他应该堵车了"or"他可能堵车了", "应该" shows that the speculation is more confident.
    – Sun Yuxian
    Commented Jul 31, 2020 at 3:20
  • Yes, you said it exactly right. "应该 shows that speculation is more confident". That's why 应该 -> should, 可能 -> probably.
    – dan
    Commented Jul 31, 2020 at 3:57

是 is used to denote something is true. 是[component 1]. Where [component 1] is true. For example, 他是睡著了(他是[component 1], where [component 1] is 睡著了)(He has fallen asleep.) Because [component 1] is true, 睡著了(has fallen asleep) is true. We get 他是睡著了 means "He has fallen asleep."

應該 is used to denote something is possibly true. 應該[component 2]. Where [component 2] is possibly true. For example, 他應該會成功(他應該[component 2], where [component 2] is 會成功)(He may be successful.) Because [component 2] is possibly true, 會(denote something can happen or be true)成功(successful) is possibly true. We get 他應該會成功 means "He may be successful."

Although 是 and 應該 is independent, they can be used together. In your example, 我應該是感冒了(我應該[component 2], where [component 2] is 是[component 1], where [component 1] is 感冒了)(I possibly caught a cold.) Because [component 1] is true, 感冒了(caught a cold) is true. Because [component 2] is possibly true, 是感冒了(caught a cold) is possibly true. We get 我應該是感冒了 means "I possibly caught a cold."


"是" here gives the reader a sense of "文绉绉", and has more literariness. We don't use it that way in spoken chinese. But It's very common in literature.

For a sentence, Shorter(without "是") means more efficient, like a soldier, and longer(with "是") means more emotional, like a literary writer.

On the other hand, our college entrance examination requires more than 800 words. If we write one more "是", we will meet the requirements more easily. ^_^



I must have caught a cold

The verb 是 is the copula.

It's used to express that the subject 我 has the qualities expressed by the predicative clause 感冒了。

Now, as many other Chinese words, 感冒 doesn't have a very clear-cut grammatical role. It can be either a verb or a noun, depending on the context. What's important to note is that 感冒 can be a verbal phrase.

So if you place it after the auxiliary 应该, which introduces a verbal phrase, and remove 是, then it does assume a verbal role:


I should catch a cold

So your sentence must have the copula 是 to clarify the role of 感冒 as a property of the subject 我 (having a cold).

  • @Puco4 same as in English, "should + V" is one verbal predicate, as in "I should study", "I should exercise", etc. Whereas “should be N” is an auxiliary + copula + noun = nominal predicate. And same as in Spanish: "yo debo estudiar" vs "yo soy un estudiante"
    – blackgreen
    Commented Jul 29, 2020 at 16:04
  • @Puco4 The distinction in Chinese btw verbs and nouns is less pronounced than in English. Some words may be both depending on the context. This is such a case. If you say 应该+感冒 then 感冒 is a verb and forms a verbal predicate with 应该 "should catch a cold". So you insert 是 to make it clear that it's a nominal predicate "should be 'catch-a-cold' (constipated)"
    – blackgreen
    Commented Jul 29, 2020 at 16:12
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    Sorry for the discussion, after consulting a book I understood your point (I explained it in an answer). I just hadn't seen before this type of sentences with 是.
    – Puco4
    Commented Jul 30, 2020 at 12:18
  • 1
    @Puco4 posting an answer to your own question if you think the other ones are not fully satisfactory is a good solution
    – blackgreen
    Commented Jul 30, 2020 at 12:23

“是” express that the speaker believe he is having a cold. The sentence translated into English should be "I must be having a cold" or "I believe I'm having a cold". If without “是”, it turns out to be expressing "I should catch a cold". It doesn't make sense since nobody wants to catch a cold.

  • you are wrong, without "是", it still means "I maybe catch a cold". "应该" here should be "maybe", not "should"
    – Ticks
    Commented Jul 30, 2020 at 6:42
  • @Ticks, let me show you more examples without "是": "我应该升职了" means that "I should get promotion", "我应该离开了" means that "I should leave now". Do you agree? That's why it is confusing when you say "我应该感冒了". But you are right, most native speakers will tell by common sense that nobody would want to have cold then they can understand the "应该" is "maybe" instead of "should". That's why the "是" is needed. from better grammar perspective.
    – Tommy Pang
    Commented Jul 30, 2020 at 18:01

EDIT: As mentioned by @dan and others, now I believe the correct answer is we need 是 in the sentence to change the meaning of 应该:

应该 should (requirement) → 应该是 should be ~ might be (possibility).

Discussion for the role of 是 in the sentence without 应该:

After consulting with the book Charles N. Li, Sandra A. Thompson, Mandarin Chinese: A Functional Reference Grammar, I think I have finally understood the purpose of 是 in the sentence:


I caught a cold.

In the Edit I mentioned there were two distinct interpretations: 是 was acting as copula and 是 was for indicating emphasis (but I was referring to some mistaken structures). Now I believe the actual solution is a combination between both.

According to the book, 是 is the copula verb, which can be employed in three types of constructions:

1. Simple copula sentences: Subject + 是 + Noun phrase.

2. Special affirmative sentences: Subject + 是 + Verb phrase or 是 + Sentence.

3. Presentative sentences: Time phrase or locative phrase + 是 + noun phrase.

I believe the example could be either 1. or 2 depending on 感冒了 acting as a verb or as a noun. I will start with 2 because it feels the best interpretation.

2. Special affirmative sentences

The copula 是 (pronounced with stress) can be used to mean It is true that... or It is that... with respect to a statement already mentioned in the conversation.

For example, if we compare:


I don't have money.


It is true that I don't have money.

Without 是 the statement is neutral, we are just providing information or answering a question; but with 是 we are affirming what was previously suspected or inferred is true. 是 is still the copula verb linking the subject noun phrase to a full verb phrase. (As a side note: this use of 是 is not restricted only to link to verb phrases but it can also be placed before an entire sentence).

Probably this is the same purpose for our example if we understand 感冒了 as the verb caught a cold. The 是 is optional and it only provides an affirmation / emphasis for It is true that I caught a cold.

1. Simple copula sentences

These sentences typically have a subject that is concrete noun phrase that is linked by the copula verb 是 to a general noun phrase, which allows to identify or characterize the subject. For example:


She is my friend.

Here, the concrete subject 她 is linked to the general noun phrase 我的朋友 to indicate a trait.

However, there are some sentences called 'illogical' sentences, which can have a metaphorical meaning. For example:


Could mean I am Wang (literal), I vote for Wang (metaphorical), Wang is my favorite singer (metaphorical), I am a member of Wang's group (metaphorical), etc.



It does not mean I am a fried rice (literal), it indeed implies (e.g. in a restaurant) I am the one having the fried rice (metaphorical).

Similarly, if we understand 感冒了 catch-cold like a noun, 我是感冒了 does not mean I am a catch-cold (literal) but means I caught a cold (metaphorical).

  • Just so you know, 是 isn't your type 2 in this case. It's because 我是没钱 is valid ONLY when you put a tone emphasis on 是 when you say the sentence. In 我应该是感冒了, we don't put any emphasis on 是. We'd rather take 应该是 as a whole, denoting inferring, rekoning, etc. That's why I don't agree with those answers that stated this use of 是 is for emphasis, like 是... 的 structure.
    – dan
    Commented Jul 30, 2020 at 23:08
  • also, 我应该是感冒了 is not a metaphor from Chinese prospective, although you may get an ungrammatical sentence when you turn it into english. "I should be catch a cold." You should not use English grammar to understand Chinese.
    – dan
    Commented Jul 30, 2020 at 23:13
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    Well, this topic has been dragged too far. there is a difference between 我怎么了 and 我是怎么了. Anyways, perhaps it would be easier if you simply take {subject + 应该是xxxx} as a fixed expression for inferring something.
    – dan
    Commented Jul 31, 2020 at 11:11
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    @DanielCheung then maybe you would agree with the "Special affirmative sentences" analysis. It is more or less the same idea you gave in your answer but without using the 是...的 construction. dan considered 是 was implied in 我應該(是)感冒了 because of the meaning of 應該.
    – Puco4
    Commented Aug 2, 2020 at 8:21
  • 1
    @DanielCheung We might have to agree to disagree here. But this is my final effort. It's not 感冒, but 感冒了. We can say 我感冒了 and 我中国人, where 感冒了 and 中国人 play the same predicative role. 应该是 is for inferring. It's one's speculation, not an emphasis as in 是... 的 structure.
    – dan
    Commented Aug 2, 2020 at 8:36

Depends on the the stress.

If the stress falls on "是", "是" could be translated as "do" for a double positive. For example, I DO want a PS5.

If the stress falls on other words, the "是" could be transaled as "be" simply.

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