A **binary operation** is a mathematical operation (a.k.a. function) that takes two arguments (or inputs) and returns one output. Common examples of binary operations are addition, which takes the two addends as arguments and returns a sum, and multiplication, which takes two factors as arguments and returns a product. The word "binary" means *two*; there are also unary operations (1 argument), ternary operations (3 arguments) and more generally, *n*-ary operations (*n* arguments).