之所以

所以 suǒyǐ HSK 2 #118

therefore / so

之 zhī HSK 7 #245

possessive particle (literary equivalent of 的) / of; 's / him/her/it (literary object pronoun)

绳之以法 shéngzhīyǐfǎ #11,337

to punish according to the law / to bring to justice

诊所 zhěnsuǒ HSK 7 #3,040

clinic / doctor's office

持之以恒 chízhīyǐhéng HSK 7 #38,228

to persevere / to persist unremittingly / to keep at it

所作所为 suǒzuòsuǒwéi HSK 7 #3,554

one's actions / one's conduct / what one has done

一无所知 yīwúsuǒzhī HSK 7 #3,411

to know nothing about / to be completely ignorant of

事务所 shìwùsuǒ HSK 7 #2,797

office / firm (esp. professional services)

一无所有 yīwúsuǒyǒu HSK 7 #4,907

to have nothing / to be penniless / not to have a thing to one's name

所谓 suǒwèi HSK 7 #1,917

so-called / what is known as