是...的 (shì...de) for emphasis
Reach for this when an action is already known to have happened and you want to spotlight a specific detail about it — WHEN it happened, HOW, WHERE, WHO did it, or WHY. The 是 sits right before the detail you're highlighting, and 的 caps the sentence. It's the Chinese equivalent of a cleft sentence: 'It was yesterday that I went,' 'It was by train that we came.' Without 是...的, the sentence just reports the event; with it, you're answering an implicit question about one specific feature.
Structure
[SUBJECT] 是 [HIGHLIGHTED INFO] [VERB] (OBJECT) 的
shì... de
How to Think About It
是...的 is a spotlight, not a tense marker. The event itself is already given and shared; what's new is the detail between 是 and 的. So '我是昨天来的' answers 'when did you come?' — the coming is already established, 昨天 is the news. Try translating without the cleft: 'It's yesterday that I came.' If that English sounds right, you want 是...的; if 'I came yesterday' is enough, you don't.
Examples
我是昨天到北京的。
Wǒ shì zuótiān dào Běijīng de.
It was yesterday that I arrived in Beijing.
他是坐高铁来的。
Tā shì zuò gāotiě lái de.
It was by high-speed train that he came.
这本书是我朋友给我的。
Zhè běn shū shì wǒ péngyǒu gěi wǒ de.
It was my friend who gave me this book.
Common Mistake
Learners use 是...的 for any past action because they confuse it with a past-tense marker. It's NOT past tense — 了 is. 是...的 only works when the event is mutually known and you're highlighting a detail. If you're announcing the event itself for the first time, use 了, not 是...的.
—你做了什么？—我是昨天去北京的。 (when first reporting the trip)
—你做了什么？—我昨天去北京了。 (use 是...的 only when 'going to Beijing' is already known)
Don't Confuse With
[VERB] 了
Marks a completed action as news. Use 了 when you're TELLING someone the event happened; use 是...的 when the event is already established and you're highlighting how/when/where.
[NOUN] 是 [NOUN]
Plain 'A is B' equation. The 是 here doesn't pair with 的 and doesn't spotlight a detail — it just identifies. Don't confuse the copula 是 with the cleft 是...的.
...的 (nominalizer)
的 at the end can also turn a clause into a noun ('我说的' = 'what I said'). In 是...的 for emphasis, the 的 isn't nominalizing — it's closing the cleft frame. Context disambiguates.
Practice
Fill in: 我___昨天到北京的。
Show answer
是
Fill in: 他是坐高铁来___。
Show answer
的
Arrange: 是 / 的 / 我 / 来 / 昨天
Show answer
我是昨天来的。
Translate: It was at school that I learned this. (emphasizing where)
Show answer
我是在学校学的。
Write a 是...的 sentence highlighting WHEN or HOW you did something.
Show answer
我是去年开始学中文的。
Hear It in Real Episodes
This pattern appears in 1 Fluentide episode: