Help:Function
From Testiwiki
Function in the pyrkilo method is a special case of a variable that has its parameters defined outside the variable itself. A simple example is variable Area of a rectangle, which is defined as Width*Height. This function can used within another variable, e.g. Area of Jouni's table, which is defined as Area of a rectangle(1.5 m, 0.8 m), and the result is 1.2 m2.
Note that any variable can be used as a function by replacing its original input parameters with other parameters.