 Similarly, if I tell you that I am going to visit my aunt, I underspecify whether it is my mother’s sister or my father’s sister whom I am going to go visit. Nothing follows about the univocality or ambiguity of ‘aunt’. It simply means ‘aunt’ is true of things that are female siblings of your parent. By the same token, ‘human’ doesn’t make any demand on an person’s mass in order to be part of its extension.