ternaire

Ternaire is a French term used to describe anything based on three parts or elements. In English-language contexts the closest equivalent is ternary. The root comes from the Latin ternarius, meaning “of three.” The term can function as an adjective or a noun and appears across disciplines to indicate triadic arrangements, three-valued systems, or three-part structures.

In mathematics, logic and computer science, ternaire or ternary denotes systems, representations, or operations that involve three components. The ternary numeral system uses three basic digits, typically 0, 1, and 2. A related concept is balanced ternary, which represents digits as -1, 0, and 1 and has historical use in early computing and some analog computing circuits. In logic, ternary or three-valued logic extends beyond true and false to include a third value such as unknown or indeterminate, with several formal systems proposed by logicians like Kleene and Bochvar. The ternary conditional operator, often written as a ? b : c, is described as ternary because it selects among three expressions based on a condition; many programming languages support it as a shorthand for if-else.

In music, ternary form refers to a three-part musical structure, typically labeled ABA, where the initial section returns after a contrasting middle section. In chemistry, ternary compounds contain three different elements, and the term can also describe mixtures or systems that are triadic by design.

The word remains common in French scientific and humanities literature as a precise descriptor of triadic phenomena, distinct from binary or quaternary as used in other languages.