是 sentences
是 is a conjunctive verb that is frequently used in Chinese. It is the same as the verb “to be”.
Describing the subject
Most often, 是 
is used with a pronoun and a noun.
is used with a pronoun and a noun.Scheme
subject
who? what?
是
object
who? what?
Examples
我是医生
I'm a doctor
wǒ shì yīshēng
她是我姐姐
She's my sister
tā shì wǒ jiějie
这是词典
This is a dictionary
zhè shì cídiǎn
Denoting time or age
In declarative sentences, we may omit the verb 是 when we speak about time or age. A sentence with or without 是 are equally correct.
Scheme
subject
who? what?/when?
(是)
predicate
how much?/when?
Examples
我今年(是)十八岁
I'll be 18 years old this year
wǒ jīnnián (shì) shíbā suì
今天(是)星期五
Today is Friday
jīntiān (shì) xīngqíwǔ
However in negative sentences we must use 是.
Examples
今天不是星期五
It's not Friday
jīntiān bú shì xīngqíwǔ
Emphasizing feature of a subject
In this case, we put an adjective after 是 and add the particle 的 to the end of the sentence.
to the end of the sentence.Scheme
subject
who? what?
是
adjective
what?
的
Examples
房间是干净的
The room is clean
fángjiān shì gānjìng de
他说的是真的
What he said is true
tā shuō de shì zhēn de
If a feature of an object is not emphasized, we won't use the construction 是...的.
Compare:
房间干净 — we simply state a fact.
房间是干净的 — we emphasize the word “clean”. For example, a mother asks her daughter to clean her room, but she doesn't want to. Here, the daughter is emphasizing that the room is not dirty, so it doesn't need to be cleaned.
— we simply state a fact.
房间是干净的 — we emphasize the word “clean”. For example, a mother asks her daughter to clean her room, but she doesn't want to. Here, the daughter is emphasizing that the room is not dirty, so it doesn't need to be cleaned.Expressing possession
In this case, 是 will first be followed by a either a pronoun or a noun, and then with the possessive particle 的. Together they form a predicate that answers the question "whose".
Scheme
subject
who? what?
是
object
whose?
的
Examples
词典是我的
The dictionary is mine
cídiǎn shì wǒ de
电脑是爸爸的
The computer belongs to my father
diànnǎo shì bàba de
Confirmation of something
To express confirmation or agreement, you must put 是 between the subject and the predicate.
It can be translated as “indeed” or “really”.
Pay attention
In such cases, 是 should be emphasized verbally.
Examples
我今天是没来上课
Yes, I really didn't go to class today
wǒ jīntiān shì méi lái shàngkè
我是吃了三个包子
I won't hide it, I really ate three buns
wǒ shì chī le sān ge bāozi
Usually these sentences have the connotation an agreement or concession.
Negative sentence with 是
To make a negative sentence with 是, you should put the negative particle 不 before the verb 是.
before the verb 是.Scheme
subject
不是
complement
Pay attention
The particle 不 before the verb 是 must be pronounced with second tone bú.
Examples
我不是学生
I'm not a student
wǒ bú shì xuésheng
词典不是我的
The dictionary is not mine
cídiǎn bú shì wǒ de
Question sentences
There are two ways to ask a question in sentences with 是:
1) with the question particle 吗 at the end of the sentence.
at the end of the sentence.
Scheme
是 sentence
吗?
Examples
你是学生吗？
Are you a student?
nǐ shì xuésheng ma
她是你姐姐吗？
Is she your sister?
tā shì nǐ jiějie ma
2) with the interrogative question phrase 是不是 .
The word order here is the same as in the declarative sentence, but instead of 是 we say 是不是.
This is more colloquial type of question.
.
The word order here is the same as in the declarative sentence, but instead of 是 we say 是不是.
This is more colloquial type of question. Pay attention
The particle 吗 is not used in an interrogative question phrase.
Scheme
subject
是不是
complement?
Examples
你是不是学生？
Are you a student?
nǐ shì bú shì xuésheng
她是不是你姐姐？
Is she your sister?
tā shì bú shì nǐ jiějie ma
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