# disjunction

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**Exclusive or**— The logical operation exclusive disjunction, also called exclusive or (symbolized XOR or EOR), is a type of logical disjunction on two operands that results in a value of “true” if and only if exactly one of the operands has a value of “true”. [… …72

**Propositional calculus**— In mathematical logic, a propositional calculus or logic (also called sentential calculus or sentential logic) is a formal system in which formulas of a formal language may be interpreted as representing propositions. A system of inference rules… …73

**Boolean algebra**— This article discusses the subject referred to as Boolean algebra. For the mathematical objects, see Boolean algebra (structure). Boolean algebra, as developed in 1854 by George Boole in his book An Investigation of the Laws of Thought,[1] is a… …74

**De Morgan's laws**— In formal logic, De Morgan s laws are rules relating the logical operators and and or in terms of each other via negation. With two operands A and B: In another form: NOT (A AND B) = (NOT A) OR (NOT B) NOT (A OR B) = (NOT A) AND (NOT B) The rules …75

**Paraconsistent logic**— A paraconsistent logic is a logical system that attempts to deal with contradictions in a discriminating way. Alternatively, paraconsistent logic is the subfield of logic that is concerned with studying and developing paraconsistent (or… …76

**Method of analytic tableaux**— A graphical representation of a partially built propositional tableau In proof theory, the semantic tableau (or truth tree) is a decision procedure for sentential and related logics, and a proof procedure for formulas of first order logic. The… …77

**Boolean algebra (introduction)**— Boolean algebra, developed in 1854 by George Boole in his book An Investigation of the Laws of Thought , is a variant of ordinary algebra as taught in high school. Boolean algebra differs from ordinary algebra in three ways: in the values that… …78

**Disjunctive syllogism**— Rules of inference Propositional calculus Modus ponens (A→B, A ⊢ B) Modus tollens (A→B, ¬B ⊢ ¬A) …79

**Boolean algebras canonically defined**— Boolean algebras have been formally defined variously as a kind of lattice and as a kind of ring. This article presents them more neutrally but equally formally as simply the models of the equational theory of two values, and observes the… …80

**Logical connective**— This article is about connectives in classical logic. For connectors in natural languages, see discourse connective. For connectives and operators in other logics, see logical constant. For other logical symbols, see table of logic symbols. In… …