# Operation (mathematics)

In mathematics, an **operation** is a function which takes zero or more input values (called *operands*) to a well-defined output value. The number of operands (also known as arguments) is the arity of the operation.

The most commonly studied operations are binary operations (i.e., operations of arity 2), such as addition and multiplication, and unary operations (i.e., operations of arity 1), such as additive inverse and multiplicative inverse. An operation of arity zero, or nullary operation, is a constant.[1][2] The mixed product is an example of an operation of arity 3, also called ternary operation.

Generally, the arity is taken to be finite. However, infinitary operations are sometimes considered,[1] in which case the "usual" operations of finite arity are called **finitary operations**.

A **partial operation** is defined similarly to an operation, but with a partial function in place of a function.