fractional change of a quantity

https://doi.org/10.1351/goldbook.F02495
A term which may be expressed infinitesimally at time \(t\) by the differential \(\frac{\text{d}Q(t)}{Q(t)}\). For a finite time interval the quotient is \[\frac{\Delta Q\left(t_{1};t_{2}\right)}{Q\left(t_{1}\right)} = \frac{\left[Q\left(t_{2}\right)\,-\,Q\left(t_{1}\right)\right]}{Q\left(t_{1}\right)}\] The quantities \(Q(t_{1})\) and \(Q(t_{2})\) are of the same kind and have the same type of component. Fractional change has dimension one. Examples are: mass fractional change, \(\frac{\text{d}m(t)}{m(t)}\); @[email protected] fractional change, \(\frac{\text{d}n(t)}{n(t)}\).
Source:
PAC, 1992, 64, 1569. (Quantities and units for metabolic processes as a function of time (IUPAC Recommendations 1992)) on page 1571 [Terms] [Paper]