decay

1 of 2

verb

de·​cay di-ˈkā 

decayed; decaying; decays

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

decayer noun

decay

2 of 2

noun

1

a

: 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

Synonyms

Verb

• break down
• corrupt
• decompose
• disintegrate
• fester
• foul
• mold
• molder
• perish [chiefly British]
• putrefy
• rot
• spoil

Noun

• debilitation
• decaying
• declension
• decline
• degeneration
• descent
• deterioration
• ebbing
• enfeeblement
• weakening

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.

Recent Examples on the Web

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

Word History

Etymology

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

First Known Use

Verb

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

Noun

15th century, in the meaning defined at sense 2

Phrases Containing decay

• beta decay
• fall into decay

Kids 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 noun

1

: gradual loss of strength, soundness, health, or vigor

2

: rot entry 2 sense 1

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

transitive verb

: to destroy by decomposition

decay

2 of 2 noun

1

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)