deceleration

American  

[dee-sel-uh-rey-shuhn] / diˌsɛl əˈreɪ ʃən /

noun

1. the fact of losing speed, or the act of reducing the speed of something.

   Prolonged deceleration of the fetal heart rate is cause for concern.

2. the act or process of slowing the rate of increase of something.

   During that quarter, job creation stalled and stocks fell, confirming that there was a deceleration in the economy.

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Usage

What does deceleration mean? Deceleration describes a decrease in velocity, that is, momentum. Deceleration describes the slowing of an increase. Wind, for example, moves with a certain amount of momentum. When the wind’s momentum slows down, that is, the wind doesn’t blow as hard, we can say that the wind is experiencing deceleration. Example: The deceleration of the ship came abruptly to the passengers.

Other Word Forms

• nondeceleration noun

Etymology

Origin of deceleration

deceler(ate) ( def. ) + -ation ( def. )

Explanation

Deceleration is a slowing down: the unexpected deceleration of your car might mean that you've run out of gas. Use the noun deceleration when you talk about a gradual decrease in speed. When you're on a Ferris wheel, its deceleration tells you that the ride is almost over, and the deceleration of a train at a railroad crossing happens for safety reasons. The opposite of deceleration is acceleration, or speeding up. The word deceleration was originally an 1890's railroad term, constructed by adding de, or "the opposite of" to acceleration.

Example Sentences

Davidson’s Michael Baker said point-of-sale data in the latest week was a positive 1.3% on average, but that was a deceleration from up 3.1% the week before.

From MarketWatch • Apr. 13, 2026

Baker said the deceleration in growth shows that “gas prices may be starting to have an impact,” adding there is risk of further deceleration after tax-refund season ends.

From MarketWatch • Apr. 13, 2026

The company’s guidance points to a deceleration in growth amid competition with ByteDance’s Soda Music, Su says.

From The Wall Street Journal • Mar. 19, 2026

While Dollar General’s forecast for comparable sales growth beat expectations, it marked a deceleration from 3% growth in fiscal 2025, putting the company on track to end three years of acceleration.

From Barron's • Mar. 12, 2026

There is literally nothing I can do but hold on until, with no deceleration, we slam to a stop.

From "Catching Fire" by Suzanne Collins

Related Words

• decline
• delay
• downtrend
• downturn
• drop
• drop-off
• falloff
• slackening
• stagnation
• strike