adj. & n.
adj. 1 a of or like a question; used in questions. b Gram. (of an adjective or pronoun) asking a question (e.g. who?, which?). 2 having the form or force of a question. 3 suggesting enquiry (an interrogative tone).
n. an interrogative word (e.g. what?, why?). interrogatively adv.
[ LL interrogativus (as INTERROGATE) ]