Trying to determine the function of the interrogative pronoun "qué" in the sentence :
¿por qué está enfermo?
Stanford parsers says it is the "nominal modifier" of the adjective(?)/noun "enfermo". Freeling pretends it is the "sn" of "Por", (couldn't find the meaning of "sn")
I also thaught about considering the whole group Por qué as being an "interrogative adverb", and its function as being the "root" of the sentence ¿por qué está enfermo? or as being the "adverbial modifier" of enfermo
Can a passionate grammarian help out ? Regards