Set

　　A set is a collection of objects or things. Each object in a set a member or element of that set.Size of a set is the number of members in the set.

　　Example: 

　　The set of even numbers between 2 and 10 is of size 5:{2,4,6,8,10}.

　　The set of primes between 2 and 10 is of size 4:{2,3,5,7}.

　　Remember:

　　Each member of set A belongs to A or is in the set A.

　　A set can not have repeating member:{1,3,1,2}is not a set.

　　Rearranging the order of the members does not change the set:{1,2,3}is same as{3,2,1}.