A term which may be expressed infinitesimally at time t by the differential dQ(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, dm(t)/m(t); amount of substance fractional change, dn(t)/n(t).