因为 + reason
Reach for 因为 + reason when you just need to give a quick because-clause — usually as an answer to 'why?' or a tag onto a previous sentence. At HSK 1 level, you'll see it most often standing alone, without 所以 in the second half. 'Why are people wearing masks?' '因为有一个病毒。' That's it — short, clear, complete. Once you reach more complex sentences, you'll often pair it with 所以 in the result clause, but solo 因为 is perfectly natural for beginners and in spoken Chinese.
Structure
因为 [REASON]
yīnwèi...
How to Think About It
At HSK 1, 因为 functions like a stand-alone answer label. The 所以 half is optional in speech — speakers leave it out when the result is already obvious or stated in the previous turn. Place 因为 at the very front of the reason clause, with the rest of the sentence flowing normally after it. Don't translate English 'I did Y because X' word-for-word; in Chinese, 因为 typically opens the clause it modifies rather than sliding into the middle.
Examples
我没去，因为我病了。
Wǒ méi qù, yīnwèi wǒ bìng le.
I didn't go, because I was sick.
因为今天下雨，我们在家。
Yīnwèi jīntiān xià yǔ, wǒmen zài jiā.
Because it's raining today, we're at home.
他很开心，因为他考得很好。
Tā hěn kāixīn, yīnwèi tā kǎo de hěn hǎo.
He's very happy because he did well on the exam.
Common Mistake
Learners place 因为 in the middle of the sentence ('I went home because tired'), copying English word order. Chinese strongly prefers 因为 at the start of its clause, even when it's not paired with 所以.
我回家因为我累了。
因为我累了，所以我回家了。
Don't Confuse With
因为...所以...
Use both halves when writing complete cause-and-result sentences. Solo 因为 is fine in short answers; in longer sentences, pair it with 所以.
由于...
Formal cause marker for writing and news. 因为 is the everyday spoken default; 由于 sounds bookish in casual chat.
因为 + Noun
Use 因为 + a noun phrase ('because of the rain') for short reasons. The pattern itself is the same; just remember a full clause works too ('because it rained').
Practice
Fill in the blank: ___ 我饿了，我吃了一个苹果。
Show answer
因为
Fill in the blank: 她不来，因为她 ___ 忙。 (very)
Show answer
很
Arrange: 因为 / 下雨 / 我 / 没出门 / 了
Show answer
因为下雨了，我没出门。
Translate: I like him because he's very kind.
Show answer
我喜欢他，因为他很好。
Write a short sentence saying why you study Chinese using 因为.
Show answer
我学中文，因为我想去中国旅游。
Hear It in Real Episodes
This pattern appears in 3 Fluentide episodes: