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↔ ⇔ ≡ Logical symbolsrepresenting iff In logic and related fields such as mathematics and philosophy, if and only if (shortened iff) is a biconditional logical connective between statements. In that it is biconditional, the connective can be likened to the standard material conditional (“only if”, equal to “if … then”) combined with its reverse (“if”); hence the name. The result is that the truth of either one of the connected statements requires the truth of the other, i.e.