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:
Symbols of neglect and urban decay abound in artist Sayre Gomez’s “Precious Moments” at David Kordansky Gallery, on view through March 1.
From Los Angeles Times ● Aug. 20, 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
Mostly associated with death and decay, perhaps it is not surprising that when vultures disappeared from the skies across many West African cities, they were not missed.
From BBC ● Aug. 12, 2026
The treatment can stop decay without drilling, injections, or sedation.
From Science Daily ● Jul. 29, 2026
This method is based on the slow decay of radioactive carbon 14, a very minor component of carbon, the ubiquitous building block of life, into the nonradioactive isotope nitrogen 14.
From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond
Sphagnum moss can hold 20 times its weight in water and helps create peat bogs, where dead vegetation accumulates rather than decays, capturing carbon in the ground.
From BBC ● Feb. 8, 2026
The research team focused on detecting moments when a high-energy neutrino hits a carbon-13 nucleus and converts it into nitrogen-13, a radioactive form of nitrogen that decays roughly ten minutes later.
From Science Daily ● Dec. 12, 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
“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
“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
Teeth are the most durable part of the skeleton and often survive long after the rest of the body has decayed.
From Science Daily ● Jun. 8, 2026
Greiff points out baby heather plants nearby now able to grow in gaps left by decayed moss.
From BBC ● May 30, 2026
He had decayed before a national TV audience, a miniseries of a death.
From "Tuesdays with Morrie" by Mitch Albom
Voyager 2 and its twin, Voyager 1, rely on radioisotope thermoelectric generators, which produce electricity from heat released by decaying plutonium.
From Science Daily ● Aug. 10, 2026
Corpse flowers bloom for just 24 to 48 hours, and once opened, they reek of gym socks, rotten eggs and decaying flesh … or, well, a corpse.
From Los Angeles Times ● Jul. 10, 2026
The ornate stone balconies of the decaying colonial townhouses jutting above your head are liable to collapse at any moment.
From Barron's ● Jun. 17, 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 had seen the deer mouse, the creeping vole, the green-hued antlers of the white-tailed deer decaying underneath a cedar.
From "Snow Falling on Cedars: A Novel" by David Guterson
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.
