所以 (suǒ yǐ) means “therefore; as a result; so; the reason why”. It is an HSK 2 Chinese word in the HSK 3.0 vocabulary.
Practice each character:
他不舒服,所以没来上班。
Tā bù shūfu, suǒyǐ méi lái shàngbān.
He's not feeling well, so he didn't come to work.
Updated: 2026-05-27