Functional Dependency. Functional Dependency is the starting point for the process of normalization. Functional dependency exists when a relationship between two attributes allows you to uniquely determine the corresponding attribute’s value.If ‘X’ is known, and as a result you are able to uniquely identify ‘Y’, there is functional dependency. Combined with keys, normal forms are defined for relations.unctional dependency exists when a relationship between two attributes allows you to uniquely determine the corresponding attribute’s value. If ‘X’ is known, and as a result you are able to uniquely identify ‘Y’, there is functional dependency.