The quotient of two rates where the quantities are of the same kind in the same system
for different components:
For finite time intervals, mean rate of change ratio is:
Rate of change ratio has the dimension one. The denominator is often called the reference
quantity. Examples are: mass rate ratio,
;
amount of substance rate ratio,
.

Source:

PAC, 1992, *64*, 1569*
(Quantities and units for metabolic processes as a function of time (IUPAC Recommendations
1992))
* on page 1572