where δ δ Q is an infinitesimal amount of heat that is from the thermal reservoir interacting with the system and absorbed by the system ( δ δ Q > 0 if heat from the reservoir is absorbed by the system, and δ δ Q < 0 if heat is leaving from the system to the reservoir) and T surr is the temperature of the reservoir at a particular instant in time. Now that this is known, there must be a relation developed between the Clausius inequality and entropy. The amount of entropy S added to the system during the cycle is defined as