p-Type MethodModal expansions are hierarchical, that is, that all expansion sets less than P+1 are contained within the expansion set P+1
Nodal expansions are not hierarchical
Modal expansion typically produce finite element matrices that have a lower condition number than those produced with nodal expansions
Expansions are usually developed in one dimension. Approximation functions for multidimensional elements are constructed through tensor products of the one dimensional expansions.
Typically, the modal expansions are combined with the first order Lagrange polynomials so that continuity of the solution is satisfied between neighboring elements in a mesh