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
- Also: disintegrate (intr) physics
- (of an atomic nucleus) to undergo radioactive disintegration
- (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
- 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 removedSee also time constant
- music the fading away of a note
mid-15c., “deterioration, decline in value,” from decay (v.). Meaning “gradual decrease in radioactivity” is from 1897.
late 15c., “to decrease,” from Anglo-French decair, Old North French decair (Old French decheoir, 12c., Modern French déchoir) “to fall, set (of the sun), weaken, decline, decay,” from Vulgar Latin *decadere “to fall off,” from de- (see de-) + Latin cadere “to fall” (see case (n.1)). Meaning “decline, deteriorate” is c.1500; that of “to decompose, rot” is from 1570s. Related: Decayed; decaying.
- 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 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.