An interrogative word asks a question.
Check this site for more information.
http://spanish.about.com/od/pronouns/a/q_pronouns.htm
what is an interrogative word
2 answers
I don't see WHY on that list: ¿por qué?
WHO could be singular or plural = ?quien? OR ¿Quiénes?
Sra
WHO could be singular or plural = ?quien? OR ¿Quiénes?
Sra