The discussion explores the concept of an equation of state, particularly in relation to internal energy (U) and its dependence on pressure (P), volume (V), and temperature (T). It is established that a modified equation, such as U = cte * PV, can still qualify as an equation of state if it relates state variables. The conversation highlights that if U is expressed in terms of extensive parameters like entropy (S), volume (V), and number of particles (n), it provides comprehensive information about the system, allowing derivation of multiple equations of state. The relationship between U and T is noted as a direct linear connection. Overall, the discussion clarifies how internal energy can be integrated into the framework of equations of state.