因为 (yīnwèi) ... 所以 (suǒyǐ) ...
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, why your phone is dead.
Structure
因为 [REASON]，所以 [RESULT]
yīnwèi... suǒyǐ...
How to Think About It
Chinese keeps BOTH halves. Where English picks 'because' OR 'so', Chinese says both — leaving 所以 out makes the conclusion feel like it's hanging in the air. The pair acts as a single grammatical bracket: 因为 opens the cause, 所以 closes with the effect. Native speakers parse this as one unit, not two interchangeable words.
Examples
因为下雨，所以我没去公园。
Yīnwèi xià yǔ, 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.
Common Mistake
Learners drop 所以 because doubling 'because' and 'so' sounds redundant in English. In casual speech a native may drop one, but at HSK 1-3 keep both — your sentences will read as more complete and natural.
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 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 already established, then suggests a consequence. '既然下雨了，就别去了。' Less neutral, more conclusive.
Practice
____我饿了，所以我吃了一个苹果。
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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]
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因为我喜欢它，所以我买了。
Translate to Chinese: 'Because she likes coffee, she bought a cup.'
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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.)
Hear It in Real Episodes
This pattern appears in 1 Fluentide episode: