Let $\phi$ be a proposition with the corresponding Boolean function $f_\phi.$ Then there exist either the disjunctive or the conjunctive canonical (or both) normal forms $\operatorname{dcnf}(\phi)$ and $\operatorname{ccnf}(\phi)$ with the same Boolean functions:
$$f_\phi=f_{\operatorname{dcnf}(\phi)}=f_{\operatorname{ccnf}(\phi)}.$$
If $\operatorname{dcnf}(\phi)$ and/or $\operatorname{ccnf}(\phi)$ exist, then they are unique except of the order of literals and the minterms respectively maxterms.
Proofs: 1