The third normal form (3NF) is a normal form used in database normalization Codd's definition states that a table is in 3NF if and only if both of the following conditions hold:
- The relation R (table) is in seconfd normal form(2NF)
- Every non-prime attribute of R is non-transitively dependent on every key of R.
A non-prime attribute of R is an attribute that does not belong to any candidate key of R.
A transitive dependency is a functional dependency in which
X → Z(X determines Z) indirectly, by virtue of X → Y and Y → Z (where it is not the case that Y → X).