  The so-called Froehlich entropy is the entropy variation of a material under
the application of an electric field. This quantity can be calculated, under
suitable hypotheses, directly from the measured real part of the dielectric
function. Although Froehlich entropy is defined for a biased sample, a
straightforward physical interpretation correlates it to the state of order of
the considered physical system in absence of field. When Froehlich entropy is
calculated from experimental results, its trend is able to give several
information about the evolution in temperature of the explored compound,
especially of its phase transition features. We here provide a comprehensive
review of the physical systems (dipolar liquids and nematicons, organic
molecular crystals, metallic nanoparticles, inorganic disordered
ferroelectrics, etc.) where this approach has been exploited with the aim of
evaluating their state of order. The variety of compounds where this method has
been applied demonstrates that the estimation of the Froehlich entropy can be
considered a trustworthy tool for carrying out study on the state of order of
different classes of materials. Indeed Froehlich entropy evaluation can be
considered a fruitful and reliable investigation technique which can be
exploited alongside more usual experimental approaches.
