A Reversible Process in thermodynamics is a hypothetical process in which a system undergoes a series of changes in such a way that both the system and its surroundings can be returned to their original states without leaving any trace or causing any change in the surroundings. In essence, a reversible process is one that can be reversed without leaving any net effect on the universe. Reversible Process can be expressed as:

Where:

• $\Delta S$ is the change in entropy,
• Q rev​ is the heat added or removed in a reversible manner,
• $T$ is the temperature at which the process occurs.