A reversible process is one that can be stopped at any point and allow the system and its immediate surrounds to return to its original conditions without changing the rest of the universe. If a process occurs quasistatically and without dissipative effects, it might be reversible.
A procedure is referred to as irreversible if it does not meet the criteria for reversibility. In this instance, it is impossible to return the system and the immediate environs to their original states without also altering the rest of the cosmos. All natural processes cannot be stopped.
