The reason why: 之所以…，是因为…
Result first, cause second. 之所以 introduces a fact the listener already knows, and 是因为 supplies the explanation. It is the reverse order of 因为…所以…, and the two pairs cannot be mixed.
Structure
主语 + 之所以 + 结果，是因为／是由于 + 原因
Explanation
Chinese words in this text can be activated to show a dictionary gloss.
…… moves from cause to result. …，… does the opposite: it starts from something already on the table — a success, a decision, a well-known fact — and then explains it. That makes it the natural pattern for answering “why?” in writing: ， “The reason he succeeded is that he never gave up.” The weight of the sentence falls on the second half.
The word order is fixed. When the subject is shared it comes before , just as with : ，. The second clause starts with or ; the is part of the pattern and cannot be dropped.
Three errors account for nearly every wrong version. Putting the subject after (…). Dropping (，…). And mixing the pairs, either by answering with or by opening with and following with . Each half has exactly one partner: goes with , with .
The pattern belongs to written and formal spoken Chinese — reports, essays, speeches. In casual talk, says the same thing more lightly.
Correct
Say each one out loud before moving on. The audio is a reference pronunciation, not a model to imitate exactly — match the tone contour, not the voice.
他之所以能成功，是因为他从来不放弃。他之所以能成功，是因為他從來不放棄。
Tā (first tone, high and level) zhīsuǒyǐ (first tone, high and level) néng (second tone, rising) chénggōng, (second tone, rising) shì (fourth tone, falling) yīnwèi (first tone, high and level) tā (first tone, high and level) cónglái (second tone, rising) bú (second tone, rising) fàngqì. (fourth tone, falling)···
The reason he succeeded is that he never gives up.
这家饭馆之所以客人多，是因为菜的味道好，价格也合理。這家飯館之所以客人多，是因為菜的味道好，價格也合理。
Zhè (fourth tone, falling) jiā (first tone, high and level) fànguǎn (fourth tone, falling) zhīsuǒyǐ (first tone, high and level) kèrén (fourth tone, falling) duō, (first tone, high and level) shì (fourth tone, falling) yīnwèi (first tone, high and level) cài (fourth tone, falling) de (neutral tone) wèidao (fourth tone, falling) hǎo, (third tone, dipping) jiàgé (fourth tone, falling) yě (third tone, dipping) hélǐ. (second tone, rising)···
This restaurant is busy because the food tastes good and the prices are reasonable.
我之所以选择这个专业，是因为我对历史很感兴趣。我之所以選擇這個專業，是因為我對歷史很感興趣。
Wǒ (third tone, dipping) zhīsuǒyǐ (first tone, high and level) xuǎnzé (third tone, dipping) zhège (fourth tone, falling) zhuānyè, (first tone, high and level) shì (fourth tone, falling) yīnwèi (first tone, high and level) wǒ (third tone, dipping) duì (fourth tone, falling) lìshǐ (fourth tone, falling) hěn (third tone, dipping) gǎn (third tone, dipping) xìngqù. (fourth tone, falling)···
I chose this subject because I am very interested in history.
Incorrect — Common mistakes
These sentences are wrong. They are printed here on purpose, each one paired with the repair and the reason, because the error you can recognise is the error you stop making.
Not quite
Incorrect sentence: 之所以他迟到，是因为路上堵车。
Correct
Correct sentence: 他之所以迟到，是因为路上堵车。
Why: A shared subject comes before 之所以, as it does before 不但.
Not quite
Incorrect sentence: 他之所以没来上课，因为他生病了。
Correct
Correct sentence: 他之所以没来上课，是因为他生病了。
Why: The second half of the pattern is 是因为, not 因为 alone. The 是 cannot be dropped.
Not quite
Incorrect sentence: 因为他很努力，之所以成绩很好。
Correct
Correct sentence: 他之所以成绩很好，是因为他很努力。
Why: 因为 pairs with 所以 and 之所以 pairs with 是因为. Opening with 因为 and continuing with 之所以 mixes the two patterns.
Compared with
Most errors with this pattern are not errors about this pattern — they are a neighbouring pattern arriving at the wrong moment. Read these side by side.
因为…所以… tells a story in time order: the cause, then what it led to. 之所以…，是因为… starts from the result and looks back for the cause, so it is the better choice when the result is already known and the point of the sentence is the explanation. The meaning is the same; the emphasis is reversed.
Cause and result: 因为…所以… →Often confused with
Finding the error: saying the same thing twice
大约／大概 + 数量（不再加“左右”） ｜ 超过 + 数量（不再加“以上”） ｜ ……的原因是 + 小句（不再加“因为”“造成的”）
More →Mini quiz
Question 1 / 3Total score: 0
Fill the gap: “The reason he missed class is that he was ill.”
他之所以没来上课，___ 因为生病了。