因为...所以...
Reach for this when you want to explicitly link a reason to its result — 'because X, so Y.' It's the workhorse cause-and-effect connector in Chinese: stick the reason after 因为, the result after 所以, and you have a clean two-clause sentence anyone from HSK 1 onward will understand. Use it for everyday explanations: why you're tired, why you're late, why you didn't bring an umbrella.
Structure
因为 [REASON] 所以 [RESULT]
yīnwèi... suǒyǐ...
How to Think About It
Chinese keeps BOTH halves. In English you pick one — 'I was tired, SO I left' or 'BECAUSE I was tired, I left.' Chinese says both: '因为我累了,所以我走了.' Native speakers feel a sentence with only 因为 (no 所以) as hanging in the air — the conclusion isn't sealed. The pair acts as a single grammatical unit, not two interchangeable words.
Examples
因为下雨, 所以我没去公园。
Yīnwèi xiàyǔ, suǒyǐ wǒ méi qù gōngyuán.
Because it rained, I didn't go to the park.
因为他很忙, 所以没来。
Yīnwèi tā hěn máng, suǒyǐ méi lái.
Because he was busy, he didn't come.
因为太冷了, 所以我穿了两件毛衣。
Yīnwèi tài lěng le, suǒyǐ wǒ chuān le liǎng jiàn máoyī.
Because it was too cold, I put on two sweaters.
因为下雨，所以我没出门。
Yīnwèi xià yǔ, suǒyǐ wǒ méi chū mén.
Because it was raining, I didn't go out.
因为他工作太忙，所以没能完成这个梦想。
Yīnwèi tā gōngzuò tài máng, suǒyǐ méi néng wánchéng zhè gè mèngxiǎng.
Because his work was too busy, he wasn't able to fulfill that dream.
因为这双鞋很轻，所以现在所有的运动员都穿。
Yīnwèi zhè shuāng xié hěn qīng, suǒyǐ xiànzài suǒyǒu de yùndòngyuán dōu chuān.
Because these shoes are light, all the athletes now wear them.
因为今天下雨，所以我没去公园。
Yīnwèi jīntiān xià yǔ, suǒyǐ wǒ méi qù gōngyuán.
Because it rained today, I didn't go to the park.
因为他生病了，所以没来上班。
Yīnwèi tā shēngbìng le, suǒyǐ méi lái shàngbān.
Because he got sick, he didn't come to work.
因为这家餐厅很有名，所以人很多。
Yīnwèi zhè jiā cāntīng hěn yǒumíng, suǒyǐ rén hěn duō.
Because this restaurant is famous, there are a lot of people.
因为今天太忙了，所以我没回你的电话。
Yīnwèi jīntiān tài máng le, suǒyǐ wǒ méi huí nǐ de diànhuà.
Because today was too busy, I didn't return your call.
Common Mistake
English speakers often drop 所以 because doubling 'because' and 'so' sounds redundant in their head. In casual spoken Chinese you can drop one, but in writing and at HSK 1-3 you keep both. Always use both when you're learning — natives will read your sentence as more complete.
因为我累了, 我去睡觉了。
因为我累了, 所以我去睡觉了。
Don't Confuse With
由于...因此...
Same meaning, much more formal. Use 由于...因此... in written essays, news articles, and reports — not in everyday speech.
之所以...是因为...
Flips the order — result first, reason second ('The reason X is because Y'). Used for emphasis when you want to highlight the cause: '我之所以学中文, 是因为我喜欢中国电影.'
既然...就...
Looks similar but means 'since/given that' — it presents the reason as something already established, then suggests a consequence. '既然下雨了, 就别去了.' (Since it's raining, just don't go.) Less neutral, more conclusive.
由于...因此...
Same meaning, formal register. Use 由于...因此 in essays, reports, and news; 因为...所以 in everyday speech.
之所以...是因为...
之所以...是因为... flips the order — result first, reason after. Use it when the result is the topic everyone's wondering about, and the reason is the punchline.
Practice
___ 我饿了, 所以我吃了一个苹果。
Show answer
因为
因为他生病了, ___ 没来上课。
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所以
Put in order: [所以 / 因为 / 我 / 我 / 喜欢 / 它 / 买了]
Show answer
因为我喜欢它, 所以我买了。
Translate to Chinese: 'Because she likes coffee, she bought a cup.'
Show answer
因为她喜欢咖啡, 所以她买了一杯。
Write one sentence about why you are learning Chinese, using 因为...所以...
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Example answer: 因为我想去中国旅游, 所以我在学中文。 (Because I want to travel to China, I'm learning Chinese.)
___ 下雨，所以我没出门。
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因为
因为他很累，___ 早早睡了。
Show answer
所以
Arrange: 所以 / 因为 / 他 / 没来 / 病了
Show answer
因为他病了，所以没来。
Because I was hungry, I went to eat.
Show answer
因为我饿了，所以去吃饭了。
Explain a recent decision using 因为...所以...
Show answer
因为今天天气很好，所以我决定去公园散步。
Hear It in Real Episodes
This pattern appears in 20 Fluentide episodes. Press play to hear the sentence:
所以特别大。
So it's especially big.
Yiwu's World Cup Business — How One Chinese City Makes the Flags, Jerseys and ScarvesElementary
因为垄断对买东西的人不好。
Because monopoly is bad for people who buy things.
Ticketmaster: Why Are Concert Tickets So Expensive?Beginner
服务器受不了了。
The server couldn't handle it.
SBTI: A New Personality Test Going Viral in ChinaBeginner
因为纸做的。
Because it's made of paper.
USA: A Worker Burned His Boss's Warehouse
Related Grammar Patterns
Acquire by listening
Hear 因为...所以... in real Chinese, not in a textbook.
Fluentide picks the next news episode at your level, so this pattern shows up again and again in real context. The transcript marks it, the audio drills it. Free to start.