## change ratio of a quantity

https://doi.org/10.1351/goldbook.C00969
A term which may be expressed infinitesimally at time $$t$$ by a ratio of differentials $$\frac{\text{d}Q_{1}(t)}{\text{d}Q_{2}(t)}$$ where the kind of quantities are the same but for different components in the same system. In practice, the ratio for a finite interval is: $\frac{\Delta Q_{1}(t_{1};\,t_{2})}{\Delta Q_{2}(t_{1};t_{2})}$ Examples are: mass change ratio, $$\frac{\text{d}m_{1}(t)}{\text{d}m_{2}(t)}$$; @[email protected] change ratio, $$\frac{\text{d}n_{1}(t)}{\text{d}n_{2}(t)}$$.
Source:
PAC, 1992, 64, 1569. (Quantities and units for metabolic processes as a function of time (IUPAC Recommendations 1992)) on page 1571 [Terms] [Paper]