  I show that Modified Newtonian Dynamics (MOND) is equivalent to assuming an
isothermal dark matter density profile, with its density related to the
enclosed total baryonic mass. This density profile can be deduced by physical
laws if a dark matter core exists and if the baryonic component is
spherically-symmetric, isotropic and isothermal. All the usual predictions of
MOND, as well as the universal constant $a_0$, can be derived in this model.
Since the effects of baryonic matter are larger in galaxies than in galaxy
clusters, this result may explain why MOND appears to work well for galaxies
but poorly for clusters. As a consequence of the results presented here, MOND
can be regarded as a misinterpretation of a particular dark matter density
profile.
