Which

.  أيَّـة ُ / أيُّ both mean “which” (as a question word). The first is used for masculine while the second is used for feminine. The noun which follows either one of them has to be in the genitive case. The implication is that the two nouns create Idaafa. Please notice that أيَّـة ُ / أيُّ carry the vowel of the original case of the noun you ask about.

أيَّـة ُ مَجلـَّةٍ هذهِ؟

a. Which magazine (subject-nominative) is this?

أيَّ طالبٍ شاهدتِ؟

b. Which student (m) (object-accusative) did you (f) see?

إلی أيـَّةِ مدينةٍ سافرتَ؟

c. To which city (object of a prep.-genitive) did you travel?