The Wolfram Language usually keeps the elements of a list in exactly the order you originally entered them. If you want to treat a Wolfram Language list like a mathematical set, however, you may want to ignore the order of elements in the list.
|Union[list1,list2,…]||give a list of the distinct elements in the listi|
|Intersection[list1,list2,…]||give a list of the elements that are common to all the listi|
|Complement[universal,list1,…]||give a list of the elements that are in universal, but not in any of the listi|
|Subsets[list]||give a list of all subsets of the elements in list|
|DeleteDuplicates[list]||delete all duplicates from list|
Union gives the elements that occur in any of the lists.
Intersection gives only elements that occur in all the lists.
Complement gives elements that occur in the first list, but not in any of the others.
DeleteDuplicates deletes all duplicate elements from the list.