"internal" energy does not include the translational or rotational kinetic energy of a body "as a whole". it also does not include the relativistic mass-energy equivalent "e" = "mc"2. it excludes any potential energy a body may have because of its location in external gravitational or electrostatic field, although the potential energy it has in a field due to an induced electric or magnetic dipole moment does count, as does the energy of deformation of solids (stress-strain).