rate of change ratio

The quotient of two rates where the quantities are of the same kind in the same system for different components:
d Q 1 / d t d Q 2 / d t
For finite time intervals, mean rate of change ratio is:
Δ Q 1 / Δ t Δ Q 2 / Δ t = Δ Q 1 Δ Q 2 Δ t
Rate of change ratio has the dimension one. The denominator is often called the reference quantity. Examples are: mass rate ratio, d m 1 / d t d m 2 / d t; amount of substance rate ratio, d n 1 / d t d n 2 / d t.
PAC, 1992, 64, 1569 (Quantities and units for metabolic processes as a function of time (IUPAC Recommendations 1992)) on page 1572