Meaning of zhī suǒ yǐ:
zhī suǒ yǐ
之所以
Conjunction
(after a noun N and before a predicate P) the reason why N P; Example: 我之所以討厭他|我之所以讨厌他[wo3 zhi1suo3yi3 tao3yan4 ta1] "the reason why I dislike him (is ...)"
zhī suǒ yǐ tā néng chénggōng, shì yīnwèi tā nǔlì gōngzuò.
之所以他能成功，是因为他努力工作。
The reason why he is successful is because he works hard.
Tā zhī suǒ yǐ zhème wǎn shì yīnwèi dǔchē.
他之所以这么晚是因为堵车。
The reason why he is so late is because of a traffic jam.
