rate of change of a quantity

https://doi.org/10.1351/goldbook.R05144
The time derivative \(\frac{\text{d}Q}{\text{d}t}\) of the value of the quantity. The differential quotient may also be called derivative (or instantaneous) rate of change. Examples are: rate of change of mass, \(\frac{\text{d}m}{\text{d}t}\); rate of change of @[email protected], \(\frac{\text{d}n}{\text{d}t}\).
Source:
PAC, 1992, 64, 1569. (Quantities and units for metabolic processes as a function of time (IUPAC Recommendations 1992)) on page 1572 [Terms] [Paper]