Learn Hardcore Chinese: yīnwèi wàimiàn xiàyǔ, wǒmen bùdébù zài jiā kàn diànyǐng. - Because it’s raining outside, we have no choice but to watch a movie at home.

Breakdown of yīnwèi wàimiàn xiàyǔ, wǒmen bùdébù zài jiā kàn diànyǐng.

Why does the sentence start with 因为? Does it always mean because?

Yes. 因为 means because and introduces the reason.

In this sentence:

A very common Chinese pattern is:

But in natural speech and writing, 所以 is often omitted when the meaning is already clear. So this sentence could also be:

Both are correct.

Why is there no word for it in 外面下雨? Shouldn’t it be something like it is raining outside?

Chinese often does not use a dummy subject like English it.

In English, we say:

But in Chinese, you simply say:

So:

This is very normal in Chinese. Weather expressions often have no explicit subject.

What exactly does 外面 mean here?