deceleration
Americannoun
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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.
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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.
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
Etymology
Origin of deceleration
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.
Vocabulary lists containing deceleration
Force and Motion (Mechanics) - Middle School
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Force and Motion (Mechanics) - Introductory
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Physics - Introductory
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
However, it is a process that needs to be done smoothly with the accelerator being released gently, or it can lead to harsh deceleration.
From BBC ● Oct. 3, 2026
In addition, the analysts flag a likely deceleration in constant-currency backlog growth, estimating SAP will end the year at 24% organic growth versus the 26% figure from June.
From MarketWatch ● Aug. 26, 2026
The latest indicators from the Bank of Thailand showed a sharp deceleration in the private consumption index during the second quarter, Tay added.
From The Wall Street Journal ● Aug. 14, 2026
At lower energies, nuclear stopping initially slows the matter down, producing deceleration of up to about 500 MeV.
From Science Daily ● Aug. 3, 2026
The worst case was the deceleration an astronaut would feel if his rocket engine quit before he reached orbit, causing him to plunge back down into the atmosphere.
From "Flying to the Moon: An Astronaut's Story" by Michael Collins
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
