]> Definition

Definition

To put a set in correspondence with another means to pair off elements of the first set with those of the other one.
For example we can put the set { a , b , c } in correspondence with { 1 , 2 , 3 } by pairing a with 1 , b with 2 and c with 3.
There is not a similar correspondence of { a , b } with { 1 , 2 , 3 } , although we can form a correspondence of { a , b } with a subset of { 1 , 2 , 3 } , for example, with { 2 , 3 } .