Logical equivalence
In logic and mathematics, statements p {\displaystyle p} and q {\displaystyle q} are said to be logically equivalent if they have the same truth value in every model. The logical equivalence of p {\displaystyle p} and q {\displaystyle q} is sometimes expressed as p ≡ q {\displaystyle p\equiv q} , p :: q {\displaystyle p::q} , E p q {\displaystyle {\textsf {E}}pq} , or p ⟺ q {\displaystyle p\iff q} , depending on the notation being used.