 Welcome back. Let us look at some illustrations. Consider this example. We have a closed system, say a gas and we are trying to stir it. W stirrer we know according to our sign convention is negative. So the energy would rise. So we cool it. We keep it in contact with some cooler system and then there will be a heat transfer from the system to whatever is the surroundings. So this will be less than 0. Q will also be less than 0. And if we adjust our stirrer and the rate of heat transfer, it is possible that our system undergoes no change of state. So we are trying to mix up something. It gets warm. So we keep it in a chilled tray or chilled packet of water, maintains its temperature. So this is a situation which is definitely not adiabatic. It is definitely not reversible but it is isentropic. Why is it isentropic? Because there is no change of state and hence it is isentropic. Let us look at another example. The second example is similar to the first one but let us say that we have the system now and we maintain it in a set of adiabatic boundaries and we then stir it. Naturally in this case there will be a change of state and hence because there is a change of state and we know it is an irreversible process, it will definitely be not isentropic. It is not isentropic because of the stirrer work, it is not reversible but it is adiabatic by design. Let us take the third example. Here we have a gaseous system. Let us say it is in a cylinder piston arrangement and we keep it in contact with a reservoir at temperature say T0, thermal energy reservoir. This is our system which is also at T0 and then slowly carefully we have a quasi-static expansion and it absorbs heat but maintains its temperature. Temperature is maintained, pressure decreases if it is a gas as it expands at constant temperature pressure will decrease. So in this case we have a process which is reversible but the state is changing so it is not isentropic and definitely there is heat absorption so it is not adiabatic. So here we have illustrations of situations where just one of the three adjectives is applicable. In the first case it is only an isentropic process. It is neither adiabatic nor reversible. In the second case it is purely an adiabatic process. It is not isentropic, it is not reversible. In the third case we have a reversible process which is neither isentropic nor adiabatic. I think these three illustrations makes the appreciation of the three adjectives clear. Thank you.