 We are now going to look at thermodynamic processes or simply processes in short, because everything that we do is thermodynamic. In fact, process is a nomenclature which is nothing but a short form. So it is equivalent to a change of state and since state belongs to a system, a thermodynamic system, a process is always executed by a system. So a thermodynamic process is nothing but the change in the state of a thermodynamic system and hence the process is always executed by a thermodynamic system. And because a change is involved, the minimal thing which is required for a process is you must have a system properly defined and you must have an initial state and a final state. In a virtual way, let us say that we have a system and let me simplify its state space in a two-dimensional way. If you are comfortable, you may write pressure and volume or you may write temperature and mass whatever, this is just for illustration or you could simply write x and y, x and y could be any two properties. So the depiction of a process is initial state, final state. This is the minimal representation of a process. You must have a system, you must have an initial state and you must have a final state. Now initial state and final states are big words. So quite often we will use symbols like 1 and 2 for initial and final states or sometimes i for initial, f for final. We will mark those things down. And remember that since a change of state is involved, since process means a change of state and since a change of state is represented by a property, a process involves a change in at least one property.