rate of change of a quantity

https://doi.org/10.1351/goldbook.R05144
The time derivative dQdt 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, dmdt; rate of change of
amount of substance
, dndt.
Source:
PAC, 1992, 64, 1569. (Quantities and units for metabolic processes as a function of time (IUPAC Recommendations 1992)) on page 1572 [Terms] [Paper]