de·​cay | \di-ˈkā \

Definition of decay 

(Entry 1 of 2)

intransitive verb

1 : to decline from a sound or prosperous condition a decaying empire

2 : to decrease usually gradually in size, quantity, activity, or force The three voices … decayed and died out upon her ear.— Thomas Hardy

3 : to fall into ruin the city's decaying neighborhoods

4 : 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

5 : 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

transitive verb

1 obsolete : to cause to decay : impair infirmity that decays the wise— William Shakespeare

2 : to destroy by decomposition wood decayed by bacteria



Definition of decay (Entry 2 of 2)

1 : gradual decline in strength, soundness, or prosperity or in degree of excellence or perfection the decay of the public school system

2 : a wasting or wearing away : ruin a neighborhood that had fallen into decay

3 obsolete : destruction, death … sullen presage of your own decay.— Shakespeare

4a : 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

5 : a decline in health or vigor mental decay

6 : 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)

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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


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.


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.
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Recent Examples on the Web: Verb

Without adjustment, the quantum information stored in the beryllium ions quickly decays away. Chris Lee, Ars Technica, "An intermediary between qubits provides basis for control and scaling," 25 Nov. 2018 The neurological pathways that connected his brain to his muscle memory had been dormant and disconnected so long that the wiring had decayed, leaving him as helpless as a toddler. Lindsey Vehlewald, SELF, "We Never Got Flu Shots. Then the Flu Almost Killed My Husband," 9 Nov. 2018 In universes with a weaker weak force, neutrons would decay more slowly, leading to more helium. Charles Q. Choi,, "Why Alternate Universes Might Also Host Life Around their Stars," 26 Sep. 2018 The fallout from the collapse of the bridge, located in Genoa on a freeway linking the Italian Riviera with France, has opened a debate about Italy’s decaying infrastructure. Eric Sylvers, WSJ, "Italy, EU Spar Over Bridge Collapse," 16 Aug. 2018 Across Puerto Rico, about 2,000 customers still don't have electricity running into their homes, and thousands live in roofless houses covered by decaying blue tarps. Arelis R. Hernandez And Joel Achenbach,, "Failure of imagination hindered federal response to hurricanes that devastated Puerto Rico," 14 July 2018 The nonlinear, associative libretto by Yona Kim — who also directed the gripping staging, set in what seems to be a decaying 19th-century salon — swerves from Berlin to Moscow and from Paris to Riga. New York Times, "Hannah Arendt and Walter Benjamin Don’t Talk. They Sing.," 24 June 2018 Photo: Juan Carlos for The Wall Street Journal Farmers, merchants, bankers and business moguls have been unlikely mainstays of Mr. Ortega’s support in recent years, but now his standing with them is decaying. John Otis, WSJ, "Nicaraguan Leader’s Former Pro-Business Allies Want Him Out," 10 July 2018 Meanwhile, the freeze on new material — including tritium, an element necessary for the North to make advanced atom bombs as well as the far more powerful hydrogen bombs — would mean that the program would slowly decay. David E. Sanger, New York Times, "As Bolton Says North Korea Could Disarm in a Year, Reality Lags Promises," 1 July 2018

Recent Examples on the Web: Noun

They are made of materials—glass, rubber, steel, paper gaskets, IC circuits—that decay, erode, corrode, and die from disuse. WSJ, "1968 Jaguar E-Type Zero: Revamping the Vintage Roadster as an Electric Car," 5 Oct. 2018 What occurred there is what a lot of people’s impression of our city is, violence, urban decay, lack of economic opportunity. Nick Corasaniti, New York Times, "Trenton Grieves After a Shooting at Event That Was ‘a Beacon’," 18 June 2018 Cavities, also known as tooth decay or dental caries, are little holes in the surface of your teeth, according to the Mayo Clinic. Korin Miller, SELF, "5 Reasons Your Teeth Are So Agonizingly Sensitive," 18 Apr. 2018 Instead of a candle or traditional light strands, which throw too much heat and contribute to decay, says Buskirk, opt for flameless candles. Arricca Sansone, Country Living, "How to Keep Pumpkins From Rotting and Ruining Everything You Love About Fall," 23 Aug. 2018 As federal agencies argued over details, the local decay that Matviak was trying to prevent had already started. Christopher Flavelle,, "America’s Last-Ditch Climate Strategy of Retreat Isn’t Going So Well," 2 May 2018 James helped seal a Game 7 win with a chase-down block of Andre Iguodala, the signature moment of a career that has shown no signs of decay. Tom Withersap, Anchorage Daily News, "LA-Bron: James agrees to 4-year contract with Lakers," 2 July 2018 Narloch will perform the 1981 masterpiece Triadic Memories, a meditative excursion that’s meticulously notated but centered on the way its chords and note patterns hang in the air and decay. Peter Margasak, Chicago Reader, "Two Chicago pianists perform a pair of rarely heard masterpieces by Morton Feldman," 12 July 2018 The team of forensic anthropologists turned to a trail camera set up to monitor scavenging and decay to solve the mystery of Pig No. Rob O'dell, azcentral, "What dead pigs can teach us about missing bodies in the Arizona desert," 5 July 2018

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.

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First Known Use of decay


15th century, in the meaning defined at intransitive sense 1


15th century, in the meaning defined at sense 1

History and Etymology for decay


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


see decay entry 1

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Statistics for decay

Last Updated

10 Dec 2018

Look-up Popularity

Time Traveler for decay

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

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More Definitions for decay



English Language Learners Definition of decay

 (Entry 1 of 2)

: to be slowly destroyed by natural processes : to be slowly broken down by the natural processes that destroy a dead plant or body

: to slowly lose strength, health, etc.

of a building, area, etc. : to go slowly from a bad condition to a worse condition : to slowly enter a state of ruin



English Language Learners Definition of decay (Entry 2 of 2)

: the process or result of being slowly destroyed by natural processes

: the slow loss of strength, health, etc.

of a building, area, etc. : the process or result of going slowly from a bad condition to a worse condition


de·​cay | \di-ˈkā \
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

de·​cay | \di-ˈkā \

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)

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More from Merriam-Webster on decay

Rhyming Dictionary: Words that rhyme with decay

Thesaurus: All synonyms and antonyms for decay

Spanish Central: Translation of decay

Nglish: Translation of decay for Spanish Speakers

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

Comments on decay

What made you want to look up decay? Please tell us where you read or heard it (including the quote, if possible).


to make faulty or ineffective

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