Relation between set A & B where 1 st letter of element in B is element in A , is not a function as element b in Set A has two different image / output in Set B .
We can say that Function is a subset of Relation .
Numerical : Whether given relation is a function or not ? R = {( 1,2 ),( 2,3 ),( 3,4 ), ( 4,5 ), ( 5,6 ), ( 6,7 )}