n. The number of arguments or operands a function or operation takes. For a relation, the number of domains in the corresponding Cartesian product.
n. Valence.
The Century Dictionary and Cyclopedia
n. In chem., combining capacity, according as an element or a compound is a monad, dyad, etc.; same as valency.
Word Usage
"In 1870 Peirce published a long paper “Description of a Notation for the Logic of Relatives” in which he introduced for the first time in history, two years before Frege's Begriffschrift a complete syntax for the logic of relations of arbitrary adicity (or: arity)."