de·​cay | \ di-ˈkā How to pronounce decay (audio) \
decayed; decaying; decays

Definition of decay

 (Entry 1 of 2)

intransitive verb

1 : to undergo decomposition decaying fruit Her teeth were decaying. … most isotopes of copper decay quickly, but two are stable: Cu-63 and Cu-65.— David E. Thomas
2 : to decline in health, strength, or vigor Her mind is beginning to decay with age. believes that the moral fiber of our society is decaying
3 : to fall into ruin the city's decaying neighborhoods
4 : to decline from a sound or prosperous condition a decaying empire
5 : to decrease usually gradually in size, quantity, activity, or force The three voices … decayed and died out upon her ear.— Thomas Hardy

transitive verb

1 : to destroy by decomposition wood decayed by bacteria
2 obsolete : to cause to decay : impair Infirmity, that decays the wise …— William Shakespeare



Definition of decay (Entry 2 of 2)

1a : rot The material is … resistant to fire, decay and termites …— Jack McClintock specifically : aerobic decomposition of proteins chiefly by bacteria
b : the product of decay tooth decay
2 : gradual decline in strength, soundness, or prosperity or in degree of excellence or perfection the decay of the public school system
3 : a decline in health or vigor mental decay
4 : a wasting or wearing away : ruin a neighborhood that had fallen into decay
5 : decrease in quantity, activity, or force: such as
a chemistry : spontaneous decrease in the number of radioactive atoms in radioactive material
b physics : spontaneous disintegration (as of an atom or a particle)
6 obsolete : destruction, death … sullen presage of your own decay.— Shakespeare

Other Words from decay


decayer noun

Choose the Right Synonym for decay


decay, decompose, rot, putrefy, spoil mean to undergo destructive dissolution. decay implies a slow change from a state of soundness or perfection. a decaying mansion decompose stresses a breaking down by chemical change and when applied to organic matter a corruption. the strong odor of decomposing vegetation rot is a close synonym of decompose and often connotes foulness. fruit was left to rot in warehouses putrefy implies the rotting of animal matter and offensiveness to sight and smell. corpses putrefying on the battlefield spoil applies chiefly to the decomposition of foods. keep the ham from spoiling

Examples of decay in a Sentence

Verb the smell of decaying rubbish dead plants and leaves decayed by bacteria She believes that the moral fiber of our society is decaying. our decaying public school system The city's neighborhoods are decaying. Noun the decay of dead plants and leaves She writes about the moral decay of our society. the patient's physical and mental decay The city's neighborhoods are in slow decay. See More
Recent Examples on the Web: Verb This estimate assumes that carcasses not eaten by vultures are left to decay. Ian Rose, Scientific American, 20 Sep. 2022 The former 12-bedroom home of the Duke and Duchess of York (a wedding gift from the Queen) was sold for 15 million pounds after their divorce and left to decay. Danielle Tullo, House Beautiful, 12 Sep. 2022 With her departure, the house resigns itself to neglect and decay. Meghan Cox Gurdon, WSJ, 9 Sep. 2022 Normally nutrients taken up by plants from the soil are put back when the plants dies and decay. Jeff Lowenfels, Anchorage Daily News, 18 Aug. 2022 Well, these smaller nuclei come in the form of elements like cesium, strontium, iodide, and plutonium—all which have varying abilities to live in the environment (whether preferring air, water, or soil), and decay at different rates. Miriam Fauzia, Popular Mechanics, 17 Aug. 2022 Sun damage, rot, and wear from general use can cause wood to decay and split, posing safety risks and creating visual eyesores. Kamron Sanders, Better Homes & Gardens, 10 Aug. 2022 Roads, bridges, power stations, and water treatment plants decay at the same time as storms worsen. Glen Retief, The New Republic, 11 May 2022 The original boosters were shown to increase antibody levels to a peak about two weeks after the shot, then decay steadily over the following three months. Rachel Gutman-wei, The Atlantic, 27 Aug. 2022 Recent Examples on the Web: Noun Yes, there is decay during the winter, but your lawn won’t die because there is plenty of air (and microbial activity) in and under those leaves. Jeff Lowenfels, Anchorage Daily News, 22 Sep. 2022 But after 90 years in the great outdoors, the tower was showing signs of decay. Hannah Kingsley-ma, The New Republic, 7 Sep. 2022 Being able to compare the video footage taken during each eight-hour excursion could help determine the rate of decay, and the company is collaborating with scientists keen to identify the various species on and around the wreckage. Jennifer Ouellette, Ars Technica, 6 Sep. 2022 And there was always this constant force of decay on it because it had been forgotten over the years. Chris Gardner, The Hollywood Reporter, 13 Sep. 2022 The footage, the company said, contains evidence of decay. Saleen Martin, USA TODAY, 7 Sep. 2022 Investigators saw tire marks outside the property and took a closer look, stumbling upon the scent of decay and, behind the back stoop, Fletcher's remains. Fox News, 7 Sep. 2022 Perhaps the true dragon was a slow decay of the coöperative ethos. Nick Romeo, The New Yorker, 27 Aug. 2022 Their spread exemplifies the decay of Oxford Street. Alexander Smith, NBC News, 15 Aug. 2022 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'decay.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of decay


15th century, in the meaning defined at intransitive sense 4


15th century, in the meaning defined at sense 2

History and Etymology for decay

Verb and Noun

Middle English, from Anglo-French decaïr, from Late Latin decadere to fall, sink, from Latin de- + cadere to fall — more at chance

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Time Traveler for decay

Time Traveler

The first known use of decay was in the 15th century

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Statistics for decay

Last Updated

29 Sep 2022

Cite this Entry

“Decay.” Dictionary, Merriam-Webster, Accessed 3 Oct. 2022.

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More Definitions for decay


de·​cay | \ di-ˈkā How to pronounce decay (audio) \
decayed; decaying

Kids Definition of decay

 (Entry 1 of 2)

1 : to break down or cause to break down slowly by natural processes Fruit decayed on the ground. Sugar decays teeth.
2 : to slowly worsen in condition The old theater decayed.



Kids Definition of decay (Entry 2 of 2)

1 : the process or result of slowly breaking down by natural processes The schoolhouse being deserted soon fell to decay— Washington Irving, "Sleepy Hollow"
2 : a gradual worsening in condition a decay in manners
3 : a natural change of a radioactive element into another form of the same element or into a different element


intransitive verb
de·​cay | \ di-ˈkā How to pronounce decay (audio) \

Medical Definition of decay

 (Entry 1 of 2)

: to undergo decomposition

transitive verb

: to destroy by decomposition



Medical Definition of decay (Entry 2 of 2)

1a : rot sense 1 specifically : aerobic decomposition of proteins chiefly by bacteria
b : the product of decay
2a : spontaneous decrease in the number of radioactive atoms in radioactive material
b : spontaneous disintegration (as of an atom or a nuclear particle)

More from Merriam-Webster on decay

Nglish: Translation of decay for Spanish Speakers

Britannica English: Translation of decay for Arabic Speakers Encyclopedia article about decay


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