2-D Rectilinear Coordinate Systems
Rectilinear CS: CS that has an underlying vector space structure
Cartesian CS: Rectilinear CS whose basis vectors are all of unit length
Oblique CS: Rectilinear CS in which one or more pairs of basis vectors are not perpendicular
Orthogonal CS: CS in which whenever two coordinate curves intersect they are perpendicular at the points of intersection
Orthonormal CS: Rectilinear CS in which the basis vectors are perpendicular and are all of unit length (Cartesian + orthogonal)