idempotency law

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• Propositional formula — In propositional logic, a propositional formula is a type of syntactic formula which is well formed and has a truth value. If the values of all variables in a propositional formula are given, it determines a unique truth value. A propositional… …   Wikipedia

• Join (mathematics) — In mathematical order theory, join is a binary operation on a partially ordered set that gives the supremum (least upper bound) of its arguments, provided the least upper bound exists. The join of elements x and y is denoted x lor y. A partially… …   Wikipedia

• Meet (mathematics) — In mathematics, a meet on a set is defined either as the unique infimum (greatest lower bound) with respect to a partial order on the set, provided an infimum exists, or (abstractly) as a commutative and associative binary operation satisfying an …   Wikipedia

• Join and meet — In mathematics, join and meet are dual binary operations on the elements of a partially ordered set. A join on a set is defined as the (necessarily unique) supremum (least upper bound) with respect to a partial order on the set, provided a… …   Wikipedia

• Classical logic — identifies a class of formal logics that have been most intensively studied and most widely used. The class is sometimes called standard logic as well.[1][2] They are characterised by a number of properties:[3] Law of the excluded middle and… …   Wikipedia

• Outline of logic — The following outline is provided as an overview of and topical guide to logic: Logic – formal science of using reason, considered a branch of both philosophy and mathematics. Logic investigates and classifies the structure of statements and… …   Wikipedia

• Non-classical logic — Non classical logics (and sometimes alternative logics) is the name given to formal systems which differ in a significant way from standard logical systems such as propositional and predicate logic. There are several ways in which this is done,… …   Wikipedia

• Laws of classical logic — The laws of classical logic are a small collection of fundamental sentences of propositional logic and Boolean algebra, from which may be derived all true sentences in both of these elementary formal systems.The syntax of the laws of classical… …   Wikipedia

• Material conditional — The material conditional, also known as material implication, is a binary truth function, such that the compound sentence p→q (typically read if p then q or p implies q ) is logically equivalent to the negative compound: not (p and not q). A… …   Wikipedia

• Semilattice — In mathematics, a join semilattice (or upper semilattice) is a partially ordered set which has a join (a least upper bound) for any nonempty finite subset. Dually, a meet semilattice (or lower semilattice) is a partially ordered set which has a… …   Wikipedia