qua

Many people believe that grammar is the sine qua non of language learning.

认为学习语法在学习语言中是必可少的。

Qua father, he pitied the young man; qua judge, he condemned him.

作为之父, 他同情那个年轻; 作为法官, 他将他定罪。

Money, qua money, cannot provide happiness.

钱能给以快乐。