[ajtulloch]

I think the mathematical concept that you are looking for is that of the dual space. Essentially if you have a vector space V, you can construct a dual space V* where the elements of the dual space are functions taking elements of V to the underlying field F, and under certain conditions these spaces are isomorphic (the same) - so there is a 1:1 correspondence between elements of the vector space and the functions in the dual space.