因为…所以【yīnwèi … suǒyǐ】

因为 introduces a cause and 所以 introduces the result. The cause comes first. English uses "because" or "so" but not both; Chinese keeps both, and the sentence sounds complete with them.

Dropping one half

Either word can go on its own. 所以 alone is the everyday "so"; 因为 alone sets up the reason and lets the result follow after a comma.

因为 also answers a 为什么 question by itself.

所以 goes before the subject

所以 starts its clause. When the result has a subject, the subject comes after 所以.

• × 因为下雨，我所以没去 → 因为下雨，所以我没去

When both clauses share a subject, it can go in front of 因为 and be left out of the second clause.

Result first

English often gives the result first: "I didn't go because it rained". In Chinese that order takes 是因为, and 所以 drops out.