dreiwertigkeit

Dreiwertigkeit (German for "three-valuedness") denotes the property of having three distinct values or states. The term is used across disciplines to describe systems that extend binary distinctions to include an additional intermediate or exceptional value.

In logic, dreiwertigkeit refers to three-valued logics, which introduce a third truth value alongside "true" and "false." Early formalizations were developed in the early 20th century and later variants—such as those associated with Jan Łukasiewicz, Stephen Kleene, and Dmitri Bochvar—differ in how the third value is interpreted and how logical connectives operate. Three-valued systems are applied to model indeterminacy, partial truth, or undefinedness in semantics and the philosophy of logic.

In chemistry, dreiwertigkeit corresponds to trivalence, the characteristic of an element or ion that forms three chemical bonds or has a valence of three. Common trivalent species include aluminium (Al3+) and iron(Fe3+), whose chemical behavior is shaped by the three available valence electrons or bonding sites.

In computing and information systems, three-valued logic appears in database theory (SQL’s treatment of NULL), programming languages and specification logics to represent unknown or error states, and in research on ternary computing hardware. Across contexts, the introduction of a third value provides a formal way to capture uncertainty, partiality, or additional structural complexity beyond binary schemes.