hyperplane similarity

[gusl]

In 3D, two planes are similar if their unit normal vectors are similar (i.e. make a small angle).

What about k-dimensional hyperplanes in n dimensions?

Comments

[gustavolacerda.livejournal.com]

I'm thinking one could represent the difference between two k-planes in min(k,n-k) vectors.
.. and you would combine the angles in the different directions in a Pythagorean way to get the total angle.

[bhudson.livejournal.com]

I forget how to define the total angle, and, miraculously, the intertubes are failing me. But it usually has to do with a cone; I'm not sure how it applies in the present case.