Thus, twice the average total kinetic energy ⟨ T ⟩ equals n times the average total potential energy ⟨ V TOT ⟩. Whereas V (r) represents the potential energy between two particles of distance r, V TOT represents the total potential energy of the system, i.e., the sum of the potential energy V (r) over all pairs of particles in the system. A common example of such a system is a star held together by its own gravity, where n equals −1.