Duality in Logic

Definition

In logic, functions or relations $A$ and $B$ are considered dual if $A(\neg x)=\neg B(x)$. follows are dual

• $\forall \leftrightharpoons \exists$
• $\wedge \leftrightharpoons \vee$
• $p\leftrightharpoons \neg p$
• $<\leftrightharpoons \ge$