Logical equivalence said to be the same as logical biconditional
p
        
        ⟺
        
        q
        ≡
        (
        p
        ∧
        q
        )
        ∨
        (
        ¬
        p
        ∧
        ¬
        q
        )
      
    
    {\displaystyle p\iff q\equiv (p\wedge q)\vee (\neg p\wedge \neg q)}See also
Entailment
Equisatisfiability
If and only if
Logical biconditional
Logical equality
≡ the iff symbol (U+2261 IDENTICAL TO)
∷ the a is to b as c is to d symbol (U+2237 PROPORTION)
⇔ the double struck biconditional (U+21D4 LEFT RIGHT DOUBLE ARROW)
↔ the bidirectional arrow (U+2194 LEFT RIGHT ARROW)