Function - Covariant

A function is covariant when it commutes with the transformation, i.e.:

applying the transformation to the argument of the function has the same effect as applying the transformation to the output of the function.

See also: Function - Invariant

The orientation of the major axis of inertia of the surface is covariant under a rotation transformations, since rotating a 2D surface will affect the orientation of its major axis in exactly the same way.