decaying

UK: /dɪˈkeɪɪŋ/

WordReference Random House Learner's Dictionary of American English © 2025

de•cay /dɪˈkeɪ/   v. 

1. Microbiology to (cause to) become decomposed;
   rot: [ no obj]:
   The tree began to decay soon after it was cut down.
   [ ~ + obj]:
   Candy can decay your teeth.
2. [no obj] to decline in health or prosperity;
   deteriorate:
   The transit system is rapidly decaying.

n. [uncountable]

3. Microbiology decomposition;
   rot:
   The house is in a state of decay.
4. a gradual and continuing decline:
   the decay of standards.

de•cayed, adj.: 

decayed timber.

de•cay•ing, adj.: 

the smell of decaying vegetation.

WordReference Random House Unabridged Dictionary of American English © 2025

de•cay  (di kā′), v.i. 

1. Microbiology to become decomposed; rot:
   vegetation that was decaying.
2. to decline in excellence, prosperity, health, etc.;
   deteriorate.
3. Physics (of a radioactive nucleus) to change spontaneously into one or more different nuclei in a process in which atomic particles, as alpha particles, are emitted from the nucleus, electrons are captured or lost, or fission takes place.

v.t. 

4. Microbiology to cause to decay or decompose;
   rot:
   The dampness of the climate decayed the books.

n. 

5. Microbiology decomposition;
   rot:
   Decay made the wood unsuitable for use.
6. a gradual falling into an inferior condition;
   progressive decline:
   the decay of international relations; the decay of the Aztec civilizations.
7. decline in or loss of strength, health, intellect, etc.:
   His mental decay is distressing.
8. Physics Also called disintegration, radioactive decay. a radioactive process in which a nucleus undergoes spontaneous transformation into one or more different nuclei and simultaneously emits radiation, loses electrons, or undergoes fission.
9. Aerospace the progressive, accelerating reduction in orbital parameters, particularly apogee and perigee, of a spacecraft due to atmospheric drag.

• Vulgar Latin *cadēre, for Latin cadere; (noun, nominal) late Middle English, derivative of the verb, verbal
• Old North French decair, equivalent. to de- de- + cair to fall
• (verb, verbal) late Middle English decayen 1425–75

de•cay′a•ble, adj. 
de•cayed•ness  (di kād′nis, -kā′id-), adj.  de•cay′less, adj. 
Synonyms

• 1. degenerate, wither; putrefy.
  Decay, decompose, disintegrate, rot imply a deterioration or falling away from a sound condition.
  Decay implies either entire or partial deterioration by progressive natural changes:
  Teeth decay.
  Decompose suggests the reducing of a substance to its component elements:
  Moisture makes some chemical compounds decompose.
  Disintegrate emphasizes the breaking up, going to pieces, or wearing away of anything, so that its original wholeness is impaired:
  Rocks disintegrate.
  Rot is a stronger word than decay and is esp. applied to decaying vegetable matter, which may or may not emit offensive odors:
  Potatoes rot.
• 5. putrefaction.
• 7. deterioration, decadence, impairment, dilapidation, degeneration.

Collins Concise English Dictionary © HarperCollins Publishers::

decay / dɪˈkeɪ/ verb

1. to decline or cause to decline gradually in health, prosperity, excellence, etc; deteriorate; waste away
2. to rot or cause to rot as a result of bacterial, fungal, or chemical action; decompose
3. Also: disintegrate (intransitive) (of an atomic nucleus) to undergo radioactive disintegration
4. (of an elementary particle) to transform into two or more different elementary particles
5. (intransitive) (of a stored charge, magnetic flux, etc) to decrease gradually when the source of energy has been removed

noun

1. the process of decline, as in health, mentality, beauty, etc
2. the state brought about by this process
3. decomposition, as of vegetable matter
4. rotten or decayed matter
5. See radioactive decay
6. a spontaneous transformation of an elementary particle into two or more different particles
7. a gradual decrease of a stored charge, magnetic flux, current, etc, when the source of energy has been removed

Etymology: 15th Century: from Old Northern French decaïr, from Late Latin dēcadere, literally: to fall away, from Latin cadere to fall

deˈcayable adjective