Listable is an attribute that can be assigned to a symbol f to indicate that the function f should automatically be threaded over lists that appear as its arguments.
Listable functions are effectively applied separately to each element in a list, or to corresponding elements in each list if there is more than one list.
Most built-in mathematical functions are Listable. »
All the arguments which are lists in a Listable function must be of the same length. »
Arguments that are not lists are copied as many times as there are elements in the lists.