# deceleration

/dɪˌsɛɫɝˈeɪʃən/ (US) · /dɪsˌɛləɹˈeɪʃən/ (UK) · CEFR B2 · Noun

Source: https://englishreference.com/word/deceleration
Updated: 2026-05-30

## Definition

the process of slowing down. It is the opposite of acceleration and describes how quickly something loses speed.

For teachers: the rate at which an object slows down; the negative of acceleration. Often used in physics and engineering to describe the reduction of velocity over time.

## Examples

- The car's sudden deceleration caused the passengers to lurch forward.
- Engineers must calculate the rate of deceleration to ensure the train can stop safely within the station limits.
- While the initial acceleration of the rocket was impressive, the final phase of the mission required a controlled deceleration to enter the correct orbital path around the moon.

---

From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.