Cause and Result: 因为...所以, 由于, 因此

Explaining why something happened is something you need to do from fairly early on. Chinese has a few ways to link a cause to its result, and they differ mainly in how formal they sound.

因为...所以: the everyday pair

因为 (yīnwèi, "because") introduces the cause, and 所以 (suǒyǐ, "so" or "therefore") introduces the result. Together they form the most common cause-and-result structure in Mandarin.

因为 + [Cause], 所以 + [Result]

• 因为下雨了，所以我没去。(Yīnwèi xià yǔ le, suǒyǐ wǒ méi qù.) -- Because it rained, I didn't go.
• 因为他很努力，所以成绩很好。(Yīnwèi tā hěn nǔlì, suǒyǐ chéngjì hěn hǎo.) -- Because he works hard, his grades are good.
• 因为今天是周末，所以商店人很多。(Yīnwèi jīntiān shì zhōumò, suǒyǐ shāngdiàn rén hěn duō.) -- Because today is the weekend, the shops are crowded.

Unlike English, where you can only use "because" or "so" but not both in the same sentence, Chinese uses both 因为 and 所以 together freely and naturally. In fact, using the pair together is the most common pattern.

That said, you can drop either one if the meaning is still clear:

• 因为下雨了，我没去。-- Because it rained, I didn't go. (所以 dropped)
• 下雨了，所以我没去。-- It rained, so I didn't go. (因为 dropped)

Both are natural. Dropping 因为 and keeping 所以 is especially common in speech.

由于: a more formal "because of"

由于 (yóuyú) means much the same as 因为 but sits at a higher register. You will see it in news reports, formal writing, announcements, and official speech. It is not often heard in casual conversation.

由于 usually appears at the start of a sentence or clause and introduces the cause. It often pairs with 因此 or 所以 in the result clause.

• 由于天气原因，航班被取消了。(Yóuyú tiānqì yuányīn, hángbān bèi qǔxiāo le.) -- Due to weather conditions, the flight was cancelled.
• 由于人手不足，工作进展缓慢。(Yóuyú rénshǒu bùzú, gōngzuò jìnzhǎn huǎnmàn.) -- Due to a shortage of staff, work has been progressing slowly.

One thing to note: 由于 tends to follow more naturally before noun phrases ("due to the weather," "due to a lack of funds") whereas 因为 can comfortably introduce a full clause ("because it rained," "because he was tired"). Both work before clauses, but 由于 before a bare noun phrase sounds especially clean and formal.

因此: "therefore," pointing to the result

因此 (yīncǐ) means "therefore" or "as a result." It sits at the start of the result clause and points back to a cause that was already stated. Like 由于, it leans formal and is more common in writing than in everyday speech.

• 他缺乏经验，因此犯了一些错误。(Tā quēfá jīngyàn, yīncǐ fàn le yīxiē cuòwù.) -- He lacked experience and therefore made some mistakes.
• 这个地区缺水，因此农业发展很困难。(Zhège dìqū quē shuǐ, yīncǐ nóngyè fāzhǎn hěn kùnnan.) -- This area lacks water, so agricultural development is very difficult.

因此 and 所以 are close in meaning, but 所以 fits both spoken and written Chinese while 因此 belongs mostly to formal written contexts.

How they compare

Word	Register	Role	Common partner
因为	Everyday	Introduces the cause	所以
所以	Everyday	Introduces the result	因为
由于	Formal / written	Introduces the cause	因此 or 所以
因此	Formal / written	Introduces the result	由于

For most conversations, 因为...所以 is all you need. 由于 and 因此 are worth recognizing when you read news or formal texts, and using them yourself in writing will make your Chinese sound more polished.