HSK 2
The 是...的 Construction in Chinese
The 是...的 construction spotlights one detail — when, where, how, or who — about an action both speakers already know happened. 是 opens the frame before that detail and 的 closes it after the verb. Use it to stress the detail, not to report that something happened for the first time.
STRUCTURE
是 + time/place/manner + Verb + 的
When to use 是 — and when not
Use it when
- Stressing when a known past action happened: 我是昨天来的。
- Stressing how or where it happened: 他是坐飞机来的 / 我是在北京学的中文。
- Asking about the detail of a known event: 你是什么时候来的?
Don't use it when
- Reporting that something happened at all — that is 了's job: 我昨天买了一本书 announces the purchase; 是…的 assumes it is known and stresses a detail.
- Future or planned actions: 是…的 frames only a completed, established event.
- When you are not stressing when / where / how / who — with no such detail to highlight, use a plain sentence.
Right vs. wrong
我是昨天来了。
我是昨天来的。
Ending the frame with 了 instead of 的
Once 是 opens the frame, the sentence must close with 的, not 了. 是…的 already marks the event as completed and known, so learners who swap in 了 out of habit break the pattern.
他是坐飞机来北京。
他是坐飞机来北京的。
Using 是 but dropping 的
The frame needs both halves: 是 opens it and 的 closes it after the verb phrase. With 是 present but no 的, the sentence sounds unfinished to a native ear.
Examples
我是昨天来的。
Wǒ shì zuótiān lái de.
It was yesterday that I came.
他是坐飞机来的。
Tā shì zuò fēijī lái de.
He came by plane.
我是在北京学的中文。
Wǒ shì zài Běijīng xué de Zhōngwén.
I learned Chinese in Beijing.
你是什么时候来的?
Nǐ shì shénme shíhou lái de?
When did you come?
这本书是他买的。
Zhè běn shū shì tā mǎi de.
He's the one who bought this book.
Common mistakes
我是昨天来了。
Wǒ shì zuótiān lái le.
The 是…的 frame ends in 的, not 了: 我是昨天来的。
他是坐飞机来北京。
Tā shì zuò fēijī lái Běijīng.
是 opened the frame, so it needs 的 to close it: 他是坐飞机来北京的。
我明天是坐飞机去的。
Wǒ míngtiān shì zuò fēijī qù de.
是…的 frames only a completed, known event; a future plan uses a plain sentence: 我明天坐飞机去。
Think you've got it?
Write your own 是 sentence and check that grammar point first.
The 是...的 Construction FAQ
What is the difference between 是...的 and 了?
了 reports that something happened; 是…的 assumes everyone knows it happened and spotlights a detail — when, where, how, or who. 我买了书 tells you about the purchase, while 我是昨天买的 stresses that it was yesterday.
Can I drop 是 in a 是...的 sentence?
Often yes in positive statements: 我是昨天来的 and 我昨天来的 both work. But you can't drop 的, and in negative sentences 是 stays: 我不是昨天来的。
Where does 的 go when there is an object?
Usually right after the verb, before the object: 我是在北京学的中文. Putting it at the very end (学中文的) is also heard, but verb + 的 + object is the safe pattern.