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)
-
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:
"Because even if the particles decay in a largely uniform patten, there will always be outliers, more persistent particles, that will release radionuclides at a later point in time."
From Science Daily ● Oct. 23, 2026
“There’s a sense of mourning, of fight and of objection. There’s a tension in something that’s this beautiful that’s also about decay and destruction.”
From Los Angeles Times ● Oct. 19, 2026
Fulton Sheen likewise fiercely denounced communism and Nazism, as well as the cultural decay he believed left the West vulnerable to tyranny.
From The Wall Street Journal ● Oct. 5, 2026
The decay just hasn’t made itself known yet.
From Salon ● Oct. 2, 2026
A lot of people gave up on Newark, and the city became synonymous with urban decay, unemployment, and poverty.
From "Proud" by Ibtihaj Muhammad
Precise investigations of decays like this are one of the primary goals of the LHCb experiment, and have been since its inception in 1994.
From Science Daily ● May 26, 2026
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
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
Then the galactic astronomers are out of business, the stars cool and die, matter itself decays and the universe becomes a thin cold haze of elementary particles.
From "Cosmos" by Carl Sagan
Beneath her boots is peat, built up over thousands of years and consisting of partially decayed plants and organic matter.
From BBC ● Sep. 12, 2026
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
He believed that a large number of worlds had formed spontaneously out of diffuse matter in space, evolved and then decayed.
From "Cosmos" by Carl Sagan
True, but the alternative is what we have now: decaying buildings, no reason to maintain them, and a growing stock of potentially affordable empty apartments.
From The Wall Street Journal ● Oct. 19, 2026
The rise in C-sections was a challenge, according to the NHS Alliance, and there were inadequate operating theatres and beds in outdated and decaying buildings, posing a safety risk.
From BBC ● Oct. 19, 2026
Park advocates have long argued that the existing city allocation is inadequate, leaving neighborhoods with decaying recreation centers, deteriorating swimming pools and filthy park bathrooms.
From Los Angeles Times ● Oct. 1, 2026
Long-lived radioactive fission products keep decaying for months or even years, releasing a weak stream of particles called antineutrinos.
From Science Daily ● Aug. 14, 2026
I saw their decaying faces in my dreams.
From "Hollow City" by Ransom Riggs
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