Some Reflections about Entropy Definition and Principle.

It is shown that the variables, thermodynamic temperature and entropy, can be defined by employing the invariance of the ratio between the heats absorbed and rejected in any static cycle between two given reservoirs. The principle of entropy increase can then be stated as a general law in agreement with experience, after a direct deduction of the entropy increases produced in the universe by large classes of real processes. The concepts of reversibility and irreversibility follow as immediate consequences.