Compartment

• amount of some substance

• ideally, label as object:substance e.g. sheep_biomass

• typical units: kg, kg m-2, numbers, numbers ha-1

• exceptionally, non-substance things like height, position

• also called 'state variable’, stock, level

• unlike real compartments, can go negative

• unlike real compartments, has infinite capacity

• cannot receive an influence arrow - changes only from flows

• rate of change is the net effect of all inflows minus all outflows

• two connected compartments must have same substance, same units

• can only contain one substance