arity

n. total number of items involved in a particular relationship; number of arguments taken by a particular function (Computer Programming); number of arguments taken by a predicate (Linguistics)

In logic, mathematics, and computer science, the arity (synonyms include type, adicity, and rank) of a function or operation is the number of arguments or operands that the function takes. The arity of a relation is the number of domains in the corresponding Cartesian product. The term springs from such words as unary, binary, ternary, etc.
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<programming> The number of arguments a function or operator takes. In some languages functions may have variable arity which sometimes means their last or only argument is actually a list of arguments.
(1997-07-21)