Grammar · Chapter 38
之所以…是因为…: the reason why… is that…
A 之所以 B，是因为 C
之所以 goes before the part whose cause you want to spotlight, and the cause itself follows 是因为: 我之所以选这家餐厅，是因为它离公司很近. Like 因为…所以…, but the order is different and the cause sounds like the main point. After 之所以 you normally write the full 是因为: 他之所以迟到，是因为堵车.
Examples
- 我之所以选这家餐厅，是因为它离公司很近。 Wǒ zhīsuǒyǐ xuǎn zhè jiā cāntīng, shì yīnwèi tā lí gōngsī hěn jìn. The reason I chose this restaurant is that it is very close to the office.
- 她之所以每天早起，就是想多读一会儿书。 Tā zhīsuǒyǐ měi tiān zǎo qǐ, jiùshì xiǎng duō dú yíhuìr shū. The reason she gets up early every day is that she wants to read a little longer.
- 他之所以迟到，是因为堵车。 Tā zhīsuǒyǐ chídào, shì yīnwèi dǔchē. The reason he was late is that he got stuck in a traffic jam.