What is a function?
In mathematics, the function consists of a two-set bineri relationship that connects each element of the first set to exactly one element of the second set. From common examples, data to digital, or actual data to actual numbers are functions.
A function is a rule that combines values of a variable quantity with other variable quantity values, and does so that the price of the other variable quantity is determined by the price of the first variable quantity (i.e. a function)