decay
Americanverb (used without object)
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decays,
present (3rd person singular)
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decayed,
past participle, past
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decaying
present participle
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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)
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decays,
present (3rd person singular)
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decayed,
past participle, past
-
decaying
present participle
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:
Children living in the most deprived areas were nearly twice as likely to have tooth decay as those living in the least.
From BBC ● Sep. 9, 2026
“The first step was to understand the extent of the decay the house had endured,” as Jacobs recalled.
From MarketWatch ● Sep. 9, 2026
The soot-blackened Philadelphia he encountered, then in a state of urban decay, sparked his lifelong fascination with industrialism, destitution and the macabre.
From Los Angeles Times ● Sep. 3, 2026
They include food shortages, water contamination, plumbing stoppages, lost mail, and mental health decay, spurring some crew members to jump ship.
From Slate ● Aug. 19, 2026
I kick up the woven mat of leaves at my feet and release months and years of decay and send beetles scurrying for cover.
From "The Adoration of Jenna Fox" by Mary E. Pearson
When astatine decays, it emits alpha particles -- tiny clusters made of two protons and two neutrons -- that can release powerful, localized bursts of energy.
From Science Daily ● Nov. 11, 2025
It contains radium that decays into radon gas, which is radioactive and can cause cancer.
From Barron's ● Oct. 10, 2025
“But the U.S. Constitution is neither bone nor stone. It is an explosion of ideas. Parchment decays and ink fades, but ideas endure; they also change.”
From Los Angeles Times ● Sep. 15, 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
“His body decays in the marble tomb in the grounds of this castle, I have seen it, Potter, and he will not return!”
From "Harry Potter and the Deathly Hallows" by J.K. Rowling
Yet, despite this surge of security personnel, basic living conditions have only decayed.
From Slate ● Aug. 11, 2026
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
Greiff points out baby heather plants nearby now able to grow in gaps left by decayed moss.
From BBC ● May 30, 2026
Eventually, Laika and her spacecraft were incinerated when their orbit decayed in April 1958.
From "100 Sideways Miles" by Andrew Smith
"The smell is like decaying wood being burned – that's the characteristic smell of peat. And that peat contains decomposed wood and organic material from many different sources."
From BBC ● Sep. 6, 2026
They probably fed on humus, decaying plant material, and fungal spores.
From Science Daily ● Aug. 27, 2026
When the local economy began declining in the 1970s, the store closed its doors and sat abandoned and decaying.
From The Wall Street Journal ● Aug. 4, 2026
On the shore of a nondescript, decaying seaside town, a boat that went missing 30 years ago suddenly reappears.
From Los Angeles Times ● Jun. 19, 2026
A few of the old mansions remained, but they were deserted and decaying; some were completely imprisoned in vines.
From "Killers of the Flower Moon" by David Grann
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.
