There are different normal forms. The main ones are:
      \item \emph{Third Normal Form (3NF)}:
        the standard relational normal form 
        used in practice (and education).
    \item \emph{Boyce-Codd Normal Form (BCNF)}: 
        \item a bit more restrictive
        \item easier to define
        \item better for our intuition of good database design
      Roughly speaking, BNCF requires that \emph{all FDs are keys.}
  In rare circumstances, a relation might not have an equivalent
  BCNF form while preserving all its FDs.\\
  \remark{The 3NF normal form always exists (and preserves the FDs).}