所以 suǒyǐ

1. suǒyǐ conjunction therefore / as a result / so
   Domain: Modern Chinese 现代汉语 , Subdomain: Function Words 虚词 , Concept: Correlative 关联词
   Notes: This conjunction is often used as a connecting word in the main clause of subordinate complex sentences. It is often used in the pattern 因为…，所以… to express cause and effect (Sun 2006, loc. 2053).
2. suǒyǐ phrase that by which
   Domain: Classical Chinese 古文
   Notes: In Literary Chinese this phrase is composed of two characters, in contrast with the single word 'therefore' in modern Chinese (Pulleyblank 1995, p. 50).

Texts that the word is most frequently mentioned in

Collection	Document Title	Occurrences
Commentaries on the Four Books by Zhu Xi 朱熹《四書章句集注》	《中庸章句》 Commentary on Doctrine of the Mean	83
Guoyu 《國語》	周語下 Discourses of Zhou III	42
Old Book of Tang 《舊唐書》	卷二十二 志第二: 禮儀二 Volume 22 Treatises 2: Rites 2	36
Han Feizi 《韓非子》	詭使第四十五 Chapter 45: Absurd Encouragements	35
Xunzi 《荀子》	禮論篇第十九 Chapter 19: Discussion on Ceremony	35
Records of the Grand Historian 《史記》	《扁鵲倉公列傳》 Biographies of Bian Que and the Duke of Cang	34
Huainanzi 《淮南子》	卷二十一　要略 Chapter 21: Summary	33
The Book of Rites 《禮記》	《中庸》 The State of Equilibrium and Harmony, also known as the Doctrine of the Mean	31
Daode Jing 《道德經》	Daode Jing 《道德經》	31
Stratagems of the Warring States 《戰國策》	卷十九　趙二 Chapter 19: Zhao II	30