 In our analysis going forward, there's going to be a sequence of properties that appears a lot. It involves the same terms and it appears so frequently that we shorthand it. We abbreviate it to a logical property. A logical property here meaning that it is a combination of actual physical properties. And that is internal energy plus pressure times of volume. This appears so frequently that we give it a name and we call it H or enthalpy. And you can think of enthalpy as a representation of the total energy of the system. That's the internal energy but also it takes into account that the properties of the situation of the system, its kinetic potential energy are represented in that pressure and volume. It'll make a little bit more sense when we get into open system analysis and we start accounting for the energy of a moving mass across the boundary. But for now just think of it as a state function. It's a combination of some properties and it represents a better representation of the total energy of a situation. And it is again just a logical property because it is a shorthand for internal energy plus pressure times volume. Furthermore in some cases it is useful to express this as a specific quantity which would be specific enthalpy. That would be total enthalpy divided by mass like any other specific property that we use. And if we divide that entire phrase by mass we would get specific internal energy plus pressure times specific volume. That's our representation for enthalpy.