verb (used without object)

verb (used with object)

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


Nearby words

  1. decathlon,
  2. decating,
  3. decatur,
  4. decatur, stephen,
  5. decatyl alcohol,
  6. decay chain,
  7. decay constant,
  8. decay series,
  9. decay theory,
  10. decay time

Origin of decay

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

Related forms

Synonym study

1. 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 especially applied to decaying vegetable matter, which may or may not emit offensive odors: Potatoes rot. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for decay

British Dictionary definitions for decay



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


the process of decline, as in health, mentality, beauty, etc
the state brought about by this process
decomposition, as of vegetable matter
rotten or decayed matterthe dentist drilled out the decay
  1. See radioactive decay
  2. a spontaneous transformation of an elementary particle into two or more different particles
  3. of an excited atom or molecule, losing energy by the spontaneous emission of photons
physics a gradual decrease of a stored charge, magnetic flux, current, etc, when the source of energy has been removedSee also time constant
music the fading away of a note
Derived Formsdecayable, adjective

Word Origin for decay

C15: from Old Northern French decaïr, from Late Latin dēcadere, literally: to fall away, from Latin cadere to fall

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for decay
Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for decay




The destruction or decomposition of organic matter as a result of bacterial or fungal action; rot.
Dental caries.
The loss of information that was registered by the senses and processed into the short-term memory system.
Radioactive decay.


To break down into component parts; rot.
To disintegrate or diminish by radioactive decay.
To decline in health or vigor; waste away.

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for decay




The breaking down or rotting of organic matter through the action of bacteria, fungi, or other organisms; decomposition.
The spontaneous transformation of a relatively unstable particle into a set of new particles. For example, a pion decays spontaneously into a muon and an antineutrino. The decay of heavy or unstable atomic nuclei (such as uranium or carbon-10) into more stable nuclei and emitted particles is called radioactive decay. The study of particle decay is fundamental to subatomic physics. See more at fundamental force radioactive decay.


To undergo decay.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.