twoargument

Twoargument is a term used to describe a function, operator, or relation that takes two input values. In mathematics, such entities are more commonly called binary operations or dyadic relations, and they have arity two.

In practice, two-argument functions appear throughout computing and logic. Examples include arithmetic operators like addition and multiplication, and logical operators like conjunction. Many programming languages treat two-argument functions as curried, meaning a function of two arguments can be applied one at a time: F(x)(y). Currying and partial application are common techniques for constructing new two-argument functions from existing ones.

Not all operations require exactly two arguments; some are variadic or unary or higher-arity. In formal type systems, a two-argument function is often described by a type such as A -> B -> C in curried form or (A, B) -> C when arguments are paired together.

Historically, binary operations have been central in mathematics, dating back to early arithmetic with symbols like + and × representing two-argument operations on numbers. In logic and algebra, the study of such operations underpins structures such as groups, rings, and function algebras, where combining two inputs yields a well-defined result.

See also: binary operator, arity, currying, partial application, higher-order function, function arity.