Ternär

Ternär is an adjective used to describe things that relate to or consist of three parts or components. In German usage, the term is widely employed in science, mathematics, and the humanities to mark triadic relationships, classifications, or structures. The English cognate is ternary. The term stems from Latin ternarius, meaning containing three, related to terni, or three apiece.

In mathematics and logic, a ternary concept involves three operands or values. A ternary operation takes three inputs, such as a ? b : c in languages with a ternary conditional operator. Ternary logic extends beyond true/false to include a third value, commonly used for uncertainty or indeterminate results.

In chemistry and materials science, ternary denotes systems with three components. A ternary compound contains three different elements, and a ternary phase diagram maps the relationships among three constituents, aiding the study of stability regions and phase transitions.

In computing and information theory, ternary refers to three-valued logic or three-state storage, as well as historical work on trinary computation, and to programming constructs that operate on three operands. In databases, three-valued logic is used to handle unknown values.

In music, ternary form is a structural principle of three-part design (A-B-A), used since the early 18th century to organize melodies and sections.