De Morgan's Laws (Logic)/Disjunction

Theorem

Formulation 1

$p \lor q \dashv \vdash \neg \paren {\neg p \land \neg q}$

Formulation 2

$\vdash \paren {p \lor q} \iff \paren {\neg \paren {\neg p \land \neg q} }$

Also see

• De Morgan's Laws (Set Theory) for a set theoretic application.
• De Morgan's Laws (Predicate Logic) for a predicate logic application.