  The rovibrational kinetic energy for an arbitrary number of rigid molecules
is computed. The result has the same general form as the kinetic energy in the
molecular rovibrational Hamiltonian, although certain quantities are augmented
to account for the rotational energy of the monomers. No specific choices of
internal coordinates or body frame are made in order to accommodate the large
variety of such conventions. However, special attention is paid to how key
quantities transform when these conventions are changed. An example system is
explicitly analysed as an illustration of the formalism.
