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  2. Logical equivalence - Wikipedia

    en.wikipedia.org/wiki/Logical_equivalence

    In logic and mathematics, statements and are said to be logically equivalent if they have the same truth value in every model. [1] 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 ...

  3. If and only if - Wikipedia

    en.wikipedia.org/wiki/If_and_only_if

    The corresponding logical symbols are "", "", [6] and , [10] and sometimes "iff".These are usually treated as equivalent. However, some texts of mathematical logic (particularly those on first-order logic, rather than propositional logic) make a distinction between these, in which the first, ↔, is used as a symbol in logic formulas, while ⇔ is used in reasoning about those logic formulas ...

  4. Contraposition - Wikipedia

    en.wikipedia.org/wiki/Contraposition

    In logic and mathematics, contraposition, or transposition, refers to the inference of going from a conditional statement into its logically equivalent contrapositive, and an associated proof method known as § Proof by contrapositive. The contrapositive of a statement has its antecedent and consequent inverted and flipped.

  5. List of logic symbols - Wikipedia

    en.wikipedia.org/wiki/List_of_logic_symbols

    propositional logic, Boolean algebra: The statement ... logical equivalence: is logically equivalent to ... for example “āŒœGāŒ” denotes the Gödel number of G ...

  6. Logical biconditional - Wikipedia

    en.wikipedia.org/wiki/Logical_biconditional

    Venn diagram of (true part in red) In logic and mathematics, the logical biconditional, also known as material biconditional or equivalence or biimplication or bientailment, is the logical connective used to conjoin two statements and to form the statement "if and only if" (often abbreviated as "iff " [1]), where is known as the antecedent, and the consequent.

  7. Glossary of logic - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_logic

    A logical principle that states that a conditional statement is logically equivalent to its contrapositive, transforming "If P, then Q" into "If not Q, then not P". contrapositive The statement resulting from swapping the antecedent and consequent of a conditional statement and negating both, maintaining logical equivalence. contrary

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  9. Material implication (rule of inference) - Wikipedia

    en.wikipedia.org/wiki/Material_implication_(rule...

    In propositional logic, material implication [1] [2] is a valid rule of replacement that allows a conditional statement to be replaced by a disjunction in which the antecedent is negated. The rule states that P implies Q is logically equivalent to not- P {\displaystyle P} or Q {\displaystyle Q} and that either form can replace the other in ...