decay
Americanverb (used without object)
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to become decomposed; rot.
vegetation that was decaying.
- Synonyms:
- putrefy, wither, degenerate
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to decline in excellence, prosperity, health, etc.; deteriorate.
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Physics. (of a radioactive nucleus) to change spontaneously into one or more different nuclei in a process in which atomic particles, as alpha particles, are emitted from the nucleus, electrons are captured or lost, or fission takes place.
verb (used with object)
noun
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Decay made the wood unsuitable for use.
- Synonyms:
- putrefaction
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a gradual falling into an inferior condition; progressive decline.
the decay of international relations; the decay of the Aztec civilizations.
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decline in or loss of strength, health, intellect, etc..
His mental decay is distressing.
- Synonyms:
- degeneration, dilapidation, impairment, decadence, deterioration
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Physics. radioactive decay.
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Aerospace. the progressive, accelerating reduction in orbital parameters, particularly apogee and perigee, of a spacecraft due to atmospheric drag.
verb
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to decline or cause to decline gradually in health, prosperity, excellence, etc; deteriorate; waste away
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to rot or cause to rot as a result of bacterial, fungal, or chemical action; decompose
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Also: disintegrate. (intr) physics
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(of an atomic nucleus) to undergo radioactive disintegration
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(of an elementary particle) to transform into two or more different elementary particles
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(intr) physics (of a stored charge, magnetic flux, etc) to decrease gradually when the source of energy has been removed
noun
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the process of decline, as in health, mentality, beauty, etc
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the state brought about by this process
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decomposition, as of vegetable matter
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rotten or decayed matter
the dentist drilled out the decay
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physics
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a spontaneous transformation of an elementary particle into two or more different particles
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of an excited atom or molecule, losing energy by the spontaneous emission of photons
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physics a gradual decrease of a stored charge, magnetic flux, current, etc, when the source of energy has been removed See also time constant
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music the fading away of a note
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The breaking down or rotting of organic matter through the action of bacteria, fungi, or other organisms; decomposition.
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The spontaneous transformation of a relatively unstable particle into a set of new particles. For example, a pion decays spontaneously into a muon and an antineutrino. The decay of heavy or unstable atomic nuclei (such as uranium or carbon-10) into more stable nuclei and emitted particles is called radioactive decay. The study of particle decay is fundamental to subatomic physics.
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See more at fundamental force radioactive decay
Synonym Usage
Decay, decompose, disintegrate, rot imply a deterioration or falling away from a sound condition. Decay implies either entire or partial deterioration by progressive natural changes: Teeth decay. Decompose suggests the reducing of a substance to its component elements: Moisture makes some chemical compounds decompose. Disintegrate emphasizes the breaking up, going to pieces, or wearing away of anything, so that its original wholeness is impaired: Rocks disintegrate. Rot is a stronger word than decay and is especially applied to decaying vegetable matter, which may or may not emit offensive odors: Potatoes rot.
Other Word Forms
Derived Forms
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semidecaynoun
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redecayverb
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decayableadjective
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decayednessadjective
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decaylessadjective
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nondecayedadjective
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nondecayingadjective
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semidecayedadjective
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undecayableadjective
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undecayedadjective
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undecayingadjective
Inflected Forms
Participles
Conjugated Forms
Present
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decaysimple
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decayssimple
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have decayedperfect
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has decayedperfect
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am decayingprogressive
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are decayingprogressive
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is decayingprogressive
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have been decayingperfect progressive
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has been decayingperfect progressive
Past
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decayedsimple
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had decayedperfect
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was decayingprogressive
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were decayingprogressive
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had been decayingperfect progressive
Future
Etymology
Origin of decay
First recorded in 1425–75; late Middle English verb decayen, decaien, from Old North French decair, equivalent to de- “down” + cair “to fall,” from unattested Vulgar Latin cadēre, for Latin cadere; noun derivative of the verb; see de-.
Explanation
To decay means to rot, decompose, break down. Our bodies—anything organic—will decay after death. Broken sidewalks, potholes, graffiti are all signs of urban decay. Tooth decay is something to avoid. Decay can also mean decline. Anyone, even a great athlete, must exercise regularly to maintain muscle tone—as soon as you stop, the muscles begin to decay. If the strength of the cable signal coming into your house grows weaker over time, you can complain that it has decayed.
Vocabulary lists containing decay
Earth Science - Middle School
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Rocks and Minerals - Introductory
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Earth Science: Natural Resources and the Environment
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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.
See Examples For:
Enamel damage is one of the major factors behind tooth decay and other dental conditions that affect almost 50% of the global population.
From Science Daily ● Jul. 23, 2026
The “Obsession” score is an ingenious showcase of decay and reinvention, taking day-spa keyboard swells and wringing them out beyond recognition.
From Los Angeles Times ● Jul. 21, 2026
"Suddenly when they're out of the ground, they're out of equilibrium, and that normally means they start to decay, fall apart."
From BBC ● Jul. 11, 2026
But when a 2024 reserve study and subsequent inspections revealed extensive structural decay, the association was faced with a $600,000 repair bill, according to a report from the Foundation for Community Association Research.
From MarketWatch ● Jul. 7, 2026
Her face was right up against Hazel’s now, enough so that Hazel could smell the odor of decay that emanated from her.
From "Breadcrumbs" by Anne Ursu
It contains radium that decays into radon gas, which is radioactive and can cause cancer.
From Barron's ● Oct. 10, 2025
Keeping the truth from someone might not be outright dishonesty, but it’s a rot that decays the same way, just festering at a slower pace.
From Salon ● Apr. 18, 2025
It gets creaky and decays, eventually becoming tasty sustenance for worms.
From Los Angeles Times ● Jan. 7, 2025
In short, it's a scenario in which the universe continues to both expand and cool - while everything within it dies off, decays, and fades away.
From BBC ● Oct. 31, 2024
In order to outline all the veins, he has to use several bodies in succession, because “a single body would not last long enough”; it decays so fast it becomes unusable.
From "The Mona Lisa Vanishes" by Nicholas Day
The silver permanently turns the decayed part of the tooth dark.
From Science Daily ● Jul. 29, 2026
“Remote and hybrid work used to be a privilege, but its benefits over in-person work have decayed across the board,” Chris Martin, senior economist at Glassdoor, told MarketWatch.
From MarketWatch ● Jun. 27, 2026
Zoologists believe the animal decayed for weeks before it was fossilised and this led to the case of mistaken identity.
From BBC ● Apr. 8, 2026
In “Vaccine Flag,” a vertical banner arcs gracefully across a soft gradient of L.A. haze, but the banner’s fabric is so tattered and decayed that its advertisement for vaccines is barely legible.
From Los Angeles Times ● Feb. 16, 2026
And Siddhartha’s soul returned, died, decayed, turned into dust, experienced the troubled course of the life cycle.
From "Siddhartha" by Hermann Hesse
During the second inspection, inspectors found decaying organic waste, wastewater, food residue, unsanitary conditions that allowed the breeding of flies, as well as live and dead flies along the northern perimeter of the warehouse.
From Los Angeles Times ● Jul. 25, 2026
But in some cases, blue skies can be seen through the facades, making the decaying structures look like theater props.
From Barron's ● Jun. 17, 2026
"Millipedes were feeding on decaying mosses, decomposed slime, and primordial gunk on the surface of the Earth."
From Science Daily ● Jun. 14, 2026
NEW YORK—More than a million fans will visit New York City this month for the World Cup, and many of them will squeeze through the decaying bowels of Pennsylvania Station while they’re here.
From The Wall Street Journal ● Jun. 13, 2026
She looked from side to side at the neighbors’ unfortunate, decaying houses.
From "The Serpent King" by Jeff Zentner
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.
