Question - What do you understand by Functional dependency?
Answer -
A relation is said to be in functional dependency when one attribute uniquely defines another attribute.
For Example, R is a Relation, X and Y are two attributes. T1 and T2 are two tuples. Then,
T1[X]=T2[X] and T1[Y]=T2[Y]
Means, the value of component X uniquely define the value of component Y.
Also, X->Y means Y is functionally dependent on X.