Is there a usual distance between linear subspaces ($V,W$) of an n-dimensional normed vector space with inner product?
In the case of hyper-planes one could use the angle (based on the inner product of the vector space). What can be used in the case of subspaces with lower dimension (not necessarily equal)? e.g. $dim(V)= n-2$ and $dim(W) = n-4$