HSK 8
之所以...是因为...: Explaining Why in Chinese
之所以...是因为/是由于... states an outcome or established situation first, then identifies the reason that explains it. The construction places explanatory focus on the latter cause and often links back to prior discourse. This card covers the paired frame; independent nominal or topic uses of 之所以 and continuations such as 就在于 also exist.
STRUCTURE
之所以 + Outcome, 是因为/是由于 + Reason
When to use 之所以…是因为/是由于… — and when not
Use it when
- To name a known outcome before explaining its cause: 这次活动之所以成功，是因为大家准备得很充分。
- To connect back to a situation already mentioned and then supply its explanation.
- To focus the reader's attention on the reason, using 是因为 or the often more formal 是由于.
Don't use it when
- When you want the ordinary cause-first order; 因为...所以... presents the reason before the result.
- Do not insert 因为 inside the outcome clause or reverse 是因为 into an order that breaks the reason clause.
- Do not treat every unpaired use of 之所以 as wrong. It can form nominal or topic expressions, and 就在于 is another established continuation.
Right vs. wrong
这次活动之所以因为成功，是因为大家准备得很充分。
这次活动之所以成功，是因为大家准备得很充分。
因为 is incorrectly stacked inside the 之所以 outcome clause
The 之所以 clause states the outcome 成功. The causal marker belongs before the later reason clause, not inside the outcome.
这部电影之所以受欢迎，是内容因为很真实。
这部电影之所以受欢迎，是因为内容很真实。
是因为 is broken apart and 因为 is placed inside its clause
The reason clause is introduced by 是因为 as a unit here. Put 内容很真实 after that marker.
Examples
这次活动之所以成功，是因为大家准备得很充分。
Zhè cì huódòng zhī suǒyǐ chénggōng, shì yīnwèi dàjiā zhǔnbèi de hěn chōngfèn.
The reason this event succeeded is that everyone prepared thoroughly.
我们之所以推迟出发，是因为天气突然变坏了。
Wǒmen zhī suǒyǐ tuīchí chūfā, shì yīnwèi tiānqì tūrán biànhuài le.
The reason we delayed our departure is that the weather suddenly worsened.
这部电影之所以受欢迎，是因为故事很真实。
Zhè bù diànyǐng zhī suǒyǐ shòu huānyíng, shì yīnwèi gùshi hěn zhēnshí.
The reason this film is popular is that its story feels very real.
他之所以进步这么快，是由于每天坚持练习。
Tā zhī suǒyǐ jìnbù zhème kuài, shì yóuyú měitiān jiānchí liànxí.
The reason he improved so quickly is his consistent daily practice.
之所以选择这个方案，是因为它更符合实际情况。
Zhī suǒyǐ xuǎnzé zhège fāng'àn, shì yīnwèi tā gèng fúhé shíjì qíngkuàng.
The reason for choosing this plan is that it better fits the actual situation.
Common mistakes
这次活动之所以因为成功，是因为大家准备得很充分。
Zhè cì huódòng zhī suǒyǐ yīnwèi chénggōng, shì yīnwèi dàjiā zhǔnbèi de hěn chōngfèn.
The outcome follows 之所以 directly: 之所以成功，是因为大家准备得很充分。
这部电影之所以受欢迎，是内容因为很真实。
Zhè bù diànyǐng zhī suǒyǐ shòu huānyíng, shì nèiróng yīnwèi hěn zhēnshí.
Keep 是因为 together before the reason clause: 是因为内容很真实。
Think you've got it?
Write your own 之所以…是因为/是由于… sentence and check that grammar point first.
之所以...是因为...: Explaining Why FAQ
How is 之所以...是因为... different from 因为...所以...?
因为...所以... normally gives the cause first and then the result. 之所以...是因为... puts the outcome or known situation first and makes the following reason the explanatory focus.
Can 是由于 replace 是因为?
Yes. Both can introduce the explanation in this frame. 是由于 often sounds more formal or analytical, but the choice also depends on the surrounding sentence and register.
Must every use of 之所以 be followed by 是因为?
No. This card teaches a common paired construction, but 之所以 also has nominal and topic uses, and forms such as 之所以...就在于... are established. Those alternatives are not automatically errors.