Glossary
Extensive Variable
The value of an extensive variable (e.g., volume, mass, energy, enthalpy, electric charge, etc) depends on the size of the system. An extensive variable can be expressed as the sum of the quantities for the separate subsystems that compose the entire system.
Each extensive variable has a complementary intensive variable. For example, the variable complementing the volume is pressure.
In general, dividing one type of extensive variable by a different type of extensive variable will in general give an intensive variable. For example, mass (extensive variable) divided by volume (extensive variable) gives density (intensive variable).