Every List is a particular ordered n-tuple of items. Generally speaking, Lists are created by means of the ListFn Function, which takes any number of items as arguments and returns a List with the items in the same order. Anything, including other Lists, may be an item in a List. Note too that Lists are extensional - two lists that have the same items in the same order are identical. Note too that a List may contain no items. In that case, the List is the NullList.