decelerate

Decelerate is a verb that means to reduce speed or the rate at which something increases. In everyday language, to decelerate is to slow down; in more general terms, it can refer to reducing the pace of activity, production, or growth. The noun form deceleration denotes the act or rate of slowing down.

Etymology: The word comes from de- (reverse) + accelerare (to hasten), from Latin celer, swift. The related adjective decelerating describes an object or process undergoing slowing.

In physics, deceleration is the rate of change of velocity that opposes the direction of motion. It is a form of negative acceleration. If an object moves with speed v0 and experiences constant deceleration a (with a > 0) opposite to its motion, its speed after time t is v(t) = v0 − a t, and its distance traveled is s(t) = v0 t − 1/2 a t^2. The stopping time is t_stop = v0 / a and the stopping distance is s_stop = v0^2 / (2 a).

Practical usage: Drivers decelerate by applying brakes, which converts kinetic energy to heat. Deceleration affects stopping distance and occupant forces. In other domains, deceleration may describe slower growth or activity, such as economic deceleration when gross domestic product grows at a reduced rate. The term is also used in engineering and traffic planning, and in related forms such as the deceleration parameter in cosmology.