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)}