What Does Functional Dependency Mean?
Functional dependency is a relationship that exists when one attribute uniquely determines another attribute.
Techopedia Explains Functional Dependency
A functional dependency is trivial if Y is a subset of X. In a table with the attributes of employee name and Social Security number (SSN), employee name is functionally dependent on SSN because the SSN is unique for individual names. An SSN identifies the employee specifically, but an employee name cannot distinguish the SSN because more than one employee could have the same name.
