decay

plural decays

1. uncountableusuallybiologyRot; any processes or result of organic matter being gradually decomposed, especially by microbial action.

   tooth decay/dental decay—wood-decay fungi—bacterial decay—photochemical decay

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   I fancied at first the stuff was paraffin wax, and smashed the jar accordingly. But the odor of camphor was unmistakable. It struck me as singularly odd, that among the universal decay, this volatile substance had chanced to survive, perhaps through many thousand years.

   1895, H. G. Wells, chapter X, in The Time Machine

   He spent himself, the labour of his axe, And leave it there far from a useful fireplace To warm the frozen swamp as best it could With the slow smokeless burning of decay.

   1914, Robert Frost, The Wood-pile

2. uncountableusuallyDeterioration of condition; loss of status, quality, strength, or fortune.

   civic and moral decay—systemic decay—fall into decay—urban decay—arrested decay—memory decay

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   Although the best room of the inn, it had the melancholy aspect of grandeur in decay, and was much too vast for comfort.

   1841 February–November, Charles Dickens, “Barnaby Rudge. Chapter 10.”, in Master Humphrey’s Clock, volume II, London: Chapman & Hall, […], →OCLC

3. uncountableusuallynatural sciencesRadioactive decay; decomposition of an atom or its nucleus.

   alpha decay—gamma decay—fission decay—decay chain

   Synonyms: nuclear decay—atomic decay

4. uncountableusuallynatural sciencesParticle decay; decomposition of a sub-atomic particle.
5. uncountableusuallyContinuous decrease of a quantity.

   exponential decay—decay rate—orbital decay—decay time—decay constant—time decay

6. obsoleteuncountableusuallyOverthrow, destruction, ruin, death.

   Let’s cheere our ſouldiers to incounter him, That grieuous image of ingratitude: That fiery thirſter after Soueraigntie: […] Reſolue my Lords and louing ſouldiers now, To ſaue your king and country from decay:

   c. 1587–1588 (date written), [Christopher Marlowe], Tamburlaine the Great. […] The First Part […], 2nd edition, part 1, London: […] [R. Robinson for] Richard Iones, […], published 1592, →OCLC; reprinted as Tamburlaine the Great (A Scolar Press Facsimile), Menston, Yorkshire; London: Scolar Press, 1973, →ISBN, Act II, scene vi

7. uncountableusuallycomputingArray decay.

present singular third person decays · participle present decaying · participle past decayed · past decayed

1. intransitiveTo deteriorate, to get worse, to lose strength or health, to decline in quality.

   The pair loved to take pictures in the decaying hospital on forty-third street.

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   "The signalling at Salisbury has be replaced for safety reasons in the next handful of years. It's worn out. Last week, there was a signal cable issue near Tisbury that stopped proper running for four whole days. The system is decaying.

   2026 February 18, Paul Clifton, “West of England Line problems laid bare”, in RAIL, number 1055, page 7

   1. intransitivebusinessTo undergo bit rot, that is, gradual degradation.
   2. intransitivecomputingTo undergo software rot, that is, to fail to be updated in a changing environment, so as to eventually become legacy or obsolete.
   3. intransitivenatural sciencesTo undergo prolonged reduction in altitude (above the orbited body).

      Damaged on lift-off, Skylab was left in orbit until its orbit decayed.

      2009, Francis Lyall, Paul B. Larsen, Space Law: A Treatise, page 120

2. intransitiveTo rot, to go bad.

   The cat's body decayed rapidly.

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   The largest tree known to us is at Syon (Plate 124), which in 1904 was no less than 60 feet in height by 7 feet in girth and still a fine tree, though its trunk is decaying inside.

   1907, Henry John Elwes and Augustine Henry, The Trees of Great Britain & Ireland, Volume 2/Cladastris

3. intransitivetransitivechemistryTo change by undergoing fission, by emitting radiation, or by capturing or losing one or more electrons; to undergo radioactive decay.

   Uranium decays to radium through a long series of steps with a cumulative half-life of 4.4 billion years.

   2005, Encyclopedia of Earth Science, edited by Timothy M. Kusky, →ISBN, page 349

4. intransitivetransitivenatural sciencesTo undergo optical decay, that is, to relax to a less excited state, usually by emitting a photon or phonon.
5. intransitiveaeronauticsLoss of airspeed due to drag.
6. transitiveTo cause to rot or deteriorate.

   The extreme humidity decayed the wooden sculptures in the museum's collection in a matter of years.

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   Infirmity, that decays the wise.

   c. 1601–1602 (date written), William Shakespeare, “Twelfe Night, or What You Will”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, [Act I, scene v]

7. intransitivecomputingOf an array: to lose its type and dimensions and be reduced to a pointer, for example when passed to a function.