A plane coordinate system whose axes are not perpendicular. The 
-coordinate
of a point 
is the abscissa of its projection onto the 
-axis in the direction of the 
-axis, and the 
-coordinate is similarly determined.
Unlike in the more general case of affine coordinates, in oblique coordinates, the unit length is the same on both axes. If the Cartesian equation of a curve in a Cartesian coordinate system is applied to an oblique coordinate system, the result will be a distorted curve. For example, a circle will be transformed into an ellipse.
