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 During World War Two, it was taken over by the Air Force but a huge fire broke out in 1945 and for most of the 1950s and beyond, it was looted and left to decay. Alex Ledsom, Forbes, 1 June 2022 Remember, your job as CEO is not to protect your current business but to build newer businesses faster than the old ones decay. Kathy Caprino, Forbes, 3 June 2022 Of empires passed away; / The blood has turned their stones to rust, / Their glory to decay. cleveland, 4 July 2022 Of empires passed away; / The blood has turned their stones to rust, / Their glory to decay. Annie Lane, oregonlive, 4 July 2022 In these facilities, bodies are simply left out in the elements to decay naturally. Monique Brouillette, Popular Mechanics, 23 June 2022 Lebanon's financial crisis has caused poverty rates to soar to over 75%, its currency to freefall and its infrastructure to rapidly decay. Tamara Qiblawi, CNN, 15 May 2022 Consistent stack pressure between different parts of the battery, which are layered like a cake, helps ensure the battery doesn’t decay at different rates in different places. Eric Tegler, Popular Mechanics, 21 June 2022 At some of those old installations, there are memorial plaques in hidden corners, but the infrastructure has mostly been left to decay. New York Times, 31 May 2022 Recent Examples on the Web: Noun Unfortunately, recent increases in the Sun’s solar activity appear to have accelerated its orbital decay. Joshua Hawkins, BGR, 17 July 2022 When the dentist then pulls up the patient’s X-rays for discussion, patients can see their tooth decay outlined in red, as well as how their cavities have grown over time, for example. Alexandra S. Levine, Forbes, 17 May 2022 So physicists track the energy produced from their decay to measure the mass of W bosons. John Conway, The Conversation, 14 Apr. 2022 They are seen as symbols of urban decay by some or just as cute piglets by others. Stefano Pitrelli, Washington Post, 17 July 2022 In recent decades, dead malls have proliferated, functioning as sets for zombie flicks and inspiring chroniclers of urban decay. Los Angeles Times, 13 June 2022 Told on a human scale with three actors shape-shifting into an array of characters, this epic tale of moral decay elucidates 160 years of American capitalism through the heady rise and swift fall of Lehman Brothers. Christopher Wallenberg,, 9 June 2022 Pro-gun voices such as Texas Governor Greg Abbott, however, blamed last week's shooting and other events like it on moral decay and proliferating mental health crises that have emerged in the last decade. Dan Carson, Chron, 31 May 2022 Since taking power in 2012, Mr. Xi has waged a high-profile campaign to fight corruption and curb displays of extravagance among officials, saying that the party faced an existential battle against moral decay within its ranks. Chun Han Wong, WSJ, 19 May 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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Last Updated

12 Aug 2022

Cite this Entry

“Decay.” Dictionary, Merriam-Webster, Accessed 15 Aug. 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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