The states, or modelled variables, of a model are the sum of the number of materials of each compartment.

For instance, a model containing three compartments Stomach, Liver and Kidney and two materials Arsenic and Lead would have the following six states:

Stomach[Arsenic], Stomach[Lead], Liver[Arsenic], Liver[Lead], Kindey[Arsenic] and Kidney[Lead].

See also