Utilisateur
Question words (I assume you mean the wh-words that appear in wh-questions) belong to several different parts of speech. ‘Who’ is a pronoun. ‘Whose’ is a possessive pronoun. ‘Which’ is a determiner (not a traditional part of speech, but that’s what it is). ‘What’ can be a pronoun or a determiner. ‘Why’, ‘when’, ‘where’ and ‘how’ are adverbs; but ‘how’ is also sometimes a degree word, as in “How stupid do you think I am?”. There are none that are nouns or verbs or adjectives.
relative
relative pronouns
The students who work hard always succeed.
integrative adjective
interrogative adjective