Level 3 · Intermediate
Emphasizing details with 是…的
Subj. + 是 + Detail + Verb + 的
When something already happened and you want to spotlight WHEN, WHERE, HOW, or WHO, wrap the detail in 是…的: 我是昨天来的 "it was yesterday that I came". The event itself is old news — the sandwiched detail is the point.
This is why questions about the details of a past event use 是…的, not 了: 你是在哪里学的中文？"Where did you learn Chinese?" Answering with 了 (我昨天来了) just reports the event; 是…的 zooms in on the detail.
Examples
我是昨天来的。
我是昨天來的。
wǒ shì zuó tiān lái de
It was yesterday that I came.
你是在哪里学的中文？
你是在哪裏學的中文？
nǐ shì zài nǎ lǐ xué de zhōng wén
Where did you learn Chinese?
他们是坐飞机去的。
他們是坐飛機去的。
tā men shì zuò fēi jī qù de
They went by plane.
这个蛋糕是妈妈做的。
這個蛋糕是媽媽做的。
zhè ge dàn gāo shì mā ma zuò de
This cake was made by Mom.
Common mistakes
✗ 我是昨天来了。
✓ 我是昨天来的。
是 pairs with 的, not 了 — the 的 closes the emphasis frame.
Related grammar points
See it in a story
Read this pattern in context: Looking for Clues (Part 2) — free graded stories with tap-to-reveal pinyin and translations.
