quayoudaoicibaDictYouDict[qua 词源字典]
"as, in the capacity of," from Latin qua "where? on which side? at which place? which way? in what direction?" figuratively "how? in what manner? by what method?; to what extent? in what degree?" correlative pronominal adverb of place, from PIE *kwo-, stem of relative and interrogative pronouns (source also of Old English hwa "who;" see who).[qua etymology, qua origin, 英语词源]