The energy and entropy evolutions of two-dimensional interacting internal gravity waves and turbulence in the (x, z) plane are studied in inviscid, viscous decay and forced-dissipative numerical simulation experiments using a spectral model. In each case the entropy evolution is compared with that predicted by the eddy-damped quasinormal Markovian (EDQNM) closure formulated by Carnevale and Frederiksen (1983) for two-dimensional internal waves. Although there is no spectral gap between the internal waves and the turbulence in the experiments, we define a transition wavenumberk1such that for wave-numbersk≪k1wave motion predominates and for wavenumbersk≫k1turbulence is dominant. In both experiments in which wave motion is generated from turbulence and in which turbulence is generated from wave instability, it is found that the entropy production and energy transfers are inhibited for increased, Brunt-Väisälä frequencies or transition wavenumbers.