1) What is adiabatic availability? 2) How can the state of a system change without changing amounts of constituents or without changing parameters? 3) Does anyone really use the concept of "adiabatic availability" other than Gyftoppoulas and Paolo? I am reading the book, "Thermodynamics: Foundations and Applications" by Elias P. Gyftopoulas and Gian Paolo Beretta (Dover, 2005). The reason that I am working through this book is that I want to have an axiomatic understanding of classical thermodynamics without statistics. This book apparently is an attempt to present thermodynamics in an axiomatic manner. I approve of the approach. However, I am stumbling over the concept of adiabatic availability. On page 73 (section 5.3) the book says: Adiabatic availability is the largest amount of energy that can be transferred to a weight in a weight process without net changes in the values of amounts of constituents and parameters, <equation 5.8 given to specify "largest amount">. I thought the states of the system were uniquely determined by the amounts of constituents and parameters. Then, how can a state change without changing those amounts and parameters? The first few illustrations of "adiabatic availability" involve a battery. The battery discharges into an electric motor, doing work. However, the amounts of constituents have to change in order for the battery to discharge. Example 5.4 on page 75 is more confusing. It describes the battery with two parameters, energy and charge. When the battery changes state, it changes both parameters. So by definition, it shouldn't be determining the adiabatic availability. Yet, it does. A google search seems to indicate that there are a few contradictory versions of the definition of "adiabatic availability" around. So I need help sorting out what the concept really means. I would ignore it. However, "adiabatic availability" seems to be a critical concept in this book. I think that I could breeze through the rest of it if I can just understand questions 1 and 2.