instantaneous rate of change
The rate of change at a single instant — the limit of average rates over shrinking intervals.
The instantaneous rate of change of f at x=a is \displaystyle\lim_{h \to 0} \dfrac{f(a+h)-f(a)}{h}, the derivative f'(a) — what the average rate of change approaches as the interval shrinks to a single point.
Examples
A speedometer reading is the instantaneous rate of change of position with respect to time.
See also
Point table
Graph settings
Calculator