Definitions

Before we begin the study of thermodynamics, it pays to define a few terms we will use a lot:

System

= definite quantity of matter enclosed in boundaries

Open System

= mass can be transferred into or out of this system

Closed System

= opposite of open system

Thermally Isolated System

= no heat transfer across boundary is possible

Completely Isolated System

= no interaction with outside is possible

Heat Reservoir
or Heat Bath

= system with unlimited heat capacity, always stays at the same temperature

Equation of State (EoS)

= mathematical relationship between the thermodynamic system variables (p, V, T, $\ldots$)
Example: Ideal gas EoS: pV=NkT

Process

= change in the thermodynamic coordinates of a system

Irreversible Process

= process with unknown intermediate states

System	= definite quantity of matter enclosed in boundaries
Open System	= mass can be transferred into or out of this system
Closed System	= opposite of open system
Thermally Isolated System	= no heat transfer across boundary is possible
Completely Isolated System	= no interaction with outside is possible
Heat Reservoir or Heat Bath	= system with unlimited heat capacity, always stays at the same temperature
Equation of State (EoS)	= mathematical relationship between the thermodynamic system variables (p, V, T, $\ldots$) Example: Ideal gas EoS: pV=NkT
Process	= change in the thermodynamic coordinates of a system
Irreversible Process	= process with unknown intermediate states