verb (used without object)
to become decomposed; rot:
vegetation that was decaying.
to decline in excellence, prosperity, health, etc.; deteriorate.
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.
verb (used with object)
to cause to decay or decompose; rot:
The dampness of the climate decayed the books.
decomposition; rot:
Decay made the wood unsuitable for use.
a gradual falling into an inferior condition; progressive decline:
the decay of international relations; the decay of the Aztec civilizations.
decline in or loss of strength, health, intellect, etc.:
His mental decay is distressing.
Also called disintegration, radioactive decay. Physics. 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.
Aerospace. the progressive, accelerating reduction in orbital parameters, particularly apogee and perigee, of a spacecraft due to atmospheric drag.
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
(intransitive) (physics) Also disintegrate

(of an atomic nucleus) to undergo radioactive disintegration
(of an elementary particle) to transform into two or more different elementary particles

(intransitive) (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 matter: the dentist drilled out the decay

See radioactive decay
a spontaneous transformation of an elementary particle into two or more different particles
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 removed See also time constant
(music) the fading away of a note

decay de·cay (dĭ-kā’)

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.

v. de·cayed, de·cay·ing, de·cays

To break down into component parts; rot.

To disintegrate or diminish by radioactive decay.

To decline in health or vigor; waste away.


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.

Verb To undergo decay.

[Nuclear physics] An automatic conversion which is applied to most array-valued expressions in C; they “decay into” pointer-valued expressions pointing to the array’s first element. This term is not used in the official standard for the language.
[Jargon File]


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