this respect because they cannot be described as the union of some constituent subsystems which are endowed with their own thermodynamics, and therefore black holes are nonextensive objects.

Looking from a different perspective, phenomenological thermodynamics of macroscopic objects has a well understood theory from statistical physics where the macroscopic properties of a given body (described by the thermodynamic parameters e.g. total energy, entropy, temperature, etc.) can be uniquely obtained from the microscopic description of the system. Standard statistical descriptions, on the other hand, usually assume that long-range type interactions are negligible, i.e. that the (linear) size of the system in question is much lager than the range of the relevant interaction between the elements of the system. Under these conditions the standard local notions of mass, energy and other extensive quantities are well defined, and by applying the additive (and therefore extensive) Boltzamann–Gibbs formula: $S_{BG}=-\sum p_i\ln p_i$, for defining the system’s entropy function, the classical thermodynamic description is recovered in the macroscopic limit.

In the presence of strong gravitational fields however, and in particular when black holes are considered, the assumption of negligible long-range type interactions can not be hold, and consequently the usual definition of mass and other extensive 