A functional dependence in a relational database is a relationship between attributes (columns) in which the value of one attribute uniquely determines the value of another.
For example:
let’s consider a simplified “Customer” table with attributes “CustomerID,” “FirstName,” “LastName,” and “Email.”
If we have a functional dependency “CustomerID → Email,” it means that for each unique “CustomerID,” there is only one corresponding “Email” associated with that ID. Knowing the “CustomerID” allows us to uniquely determine the “Email” address of the customer.