Functions

Function as a word was first used by Leibniz in 1694, and Euler popularized the notation f(x) in 1734. In terms of intuitive logic a function describes a rule of correspondence between two sets (i.e.: distance as a function of time).

Looking at functions in terms of relations a function f from A to B is a relation from A to B such that if (x,y) is an element in f and (x,z) is an element in f, then y = z. And also, the Dom(f) = A.