decayed; decaying; decays
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
David E. Thomas2
: 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
Thomas Hardy1
: to destroy by decomposition
wood decayed by bacteria
2
obsolete
: to cause to decay : impair
Infirmity, that decays the wise …—William Shakespeare
William Shakespeare
decayer
noun
1
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
ShakespeareSynonyms
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.
Recent Examples on the Web
Jeff Lowenfels, Anchorage Daily News, 22 Sep. 2022
In particular, many theorists have wondered how the great complexity of life can be reconciled with the laws of thermodynamics that suggest that all systems must inevitably decay to a state of greatest disorder.
—The Physics Arxiv Blog, Discover Magazine, 29 Apr. 2022
Corinne Purtill, Los Angeles Times, 5 Nov. 2024
Adding low levels of fluoride to drinking water is widely considered one of the greatest public health achievements of the 20th century for its role in preventing tooth decay.
—Annika Kim Constantino, CNBC, 5 Nov. 2024
See all Example Sentences for decay 
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Verb
What doesn’t decay this winter can be mulched up next spring.
—Jeff Lowenfels, Anchorage Daily News, 22 Sep. 2022
In particular, many theorists have wondered how the great complexity of life can be reconciled with the laws of thermodynamics that suggest that all systems must inevitably decay to a state of greatest disorder.
—The Physics Arxiv Blog, Discover Magazine, 29 Apr. 2022
Noun
More than half of Californians and nearly 75% of U.S. residents live in communities where fluoride has been added to drinking water to prevent tooth decay, an intervention hailed by the U.S. Centers for Disease Control as one of the 20th century’s greatest public health achievements.
—Corinne Purtill, Los Angeles Times, 5 Nov. 2024
Adding low levels of fluoride to drinking water is widely considered one of the greatest public health achievements of the 20th century for its role in preventing tooth decay.
—Annika Kim Constantino, CNBC, 5 Nov. 2024
See all Example Sentences for decay
Articles Related to decay
Dictionary Entries Near decay
Cite this Entry
“Decay.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/decay. Accessed 22 Nov. 2024.
Copy CitationKids Definition
decay
1 of 2 verb
de·cay
di-ˈkā 
1
: to lose soundness, health, strength, or vigor
2
: to go through or cause to go through decomposition
a radioactive element decays
apples that decayed in storage
decay
2 of 2 noun1
: gradual loss of strength, soundness, health, or vigor
3
: a natural decrease in the number of radioactive atoms in radioactive material
Medical Definition
decay
1 of 2 intransitive verb
de·cay
di-ˈkā
: to undergo decomposition
: to destroy by decomposition
decay
2 of 2 noun1
a
: rot sense 1
specifically
: aerobic decomposition of proteins chiefly by bacteria
b
: the product of decay
2
a
: 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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