So the negative of the temperature in Kelvins multiplied by the change in entropy of the universe is equal to the change in entropy of the system. So basically, how much energy was exchanged between the system and the surroundings minus the temperature multiplied by the delta S of the system. So let's call this equation four. Now, if we take this and we basically represent this term as delta G, then this is the more common equation that you're used to seeing. So this quantity is actually Gibbs free energy. So the negative T multiplied by delta S of the universe is called Gibbs free energy.