<logic> A truth function that returns truth when its two arguments have the same truth-value, and false otherwise. Also the connective denoting this function; also the compound proposition built from this connective. Syntactically: the two propositions imply one another. Semantically: they have the same models. Also called a biconditional, or biconditional statement.
A tautologous statement of material equivalence (next).
A truth function that is true when its two arguments have the same truth-value (not necessarily the same meaning). Notation: p <=> q, or p iff q.
See also equivalence thesis partial equivalence relation.
[Glossary of First-Order Logic]
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