や (non-exclusive connecting particle)

や is a particle in Japanese that denotes a noun as being connected to a proceeding noun in a non-exclusive list. It can be used multiple times in a sentence, adding more and more nouns together when used in sequence. や here implies an incomplete list relative to the subject—there there may be other things not mentioned.

Example: pen and book (and maybe other things)

ペンや本

ペン is marked with や, connecting it to the proceeding noun in a non-exclusive list. This indicates that both are in a list that isn’t exhaustive, there may exist unmentioned items in the list.