is the fourth derivative
of the displacement vector
with respect to time
, with the first, second, and third derivatives being velocity
, and jerk
, respectively; in other words, the jounce is the rate of change of the jerk with respect to time.
Currently, there are no well accepted designations for the derivatives of jounce. The fifth and sixth derivatives of displacement as a function of time are "sometimes somewhat facetiously" referred to as "Crackle" and "Pop"; however, these terms have not gained widespread acceptance.