Affine

The function f(x)=mx is linear but the function g(x)=mx+b is not linear.

g(x) is affine.

A Real Space R^n has an origin.

An Affine Space A^n does not have an origin.

A piece of graph paper in the package is an A^2 space.

When you circle an intersection to say this point is the origin, you make it an R^2 space.

We cannot calculate the sum of two points in an affine space but we can calculate the difference between two points in an affine space.