decay

Formsdecays, decaying, decayed

Pluraldecays (some meanings)

1. 1
   rot awayverbintransitive

   Of plant or animal matter, to rot or go bad.

   Without refrigeration, the fish decayed within a day.

   Fallen logs decay slowly in cold northern forests.

   Similarrot, decompose, spoil, putrefy

2. 2
   rotten partnoununcountable

   The gradual process of rotting or decomposing, or the decomposed state that results.

   Brushing twice a day helps prevent tooth decay.

   The hikers smelled the decay before they saw the dead elk.

   Similarrot, decomposition, putrefaction

   Note

   Ecologists treat decay as the recycling stage of life: fungi, bacteria and small animals break dead matter down and return its nutrients to the soil. Medicine and dentistry use it for tissue breaking down in the body, above all in tooth decay, the everyday name for dental caries. Outside science it keeps its sensory weight, as in the "universal decay" of H. G. Wells's The Time Machine.

3. 3
   verbintransitive

   To deteriorate or decline, losing strength, health or quality.

   Tourists photograph the decaying mansions along the waterfront.

   Standards at the paper decay a little more with every round of layoffs.

   Similardeteriorate, decline, crumble, degenerate

   Oppositeimprove, flourish

4. 4
   noununcountable

   A decline in condition, or a loss of status, quality, strength or fortune.

   Critics blamed the scandal on a wider moral decay in public life.

   The once-grand hotel had fallen into decay by the 1970s.

   Similardecline, deterioration, degeneration, disrepair, ruin

   Note

   Behind the word is a fall: Latin dēcidere, "to fall away, fail, sink," from de, "down," and cadere, "to fall," reached English through Anglo-Norman decaeir, "to fall away, decline." Decadent and decadence come from the same root and share this sense's moral coloring, as in civic and moral decay. The phrase fall into decay keeps the old image alive.

5. 5
   verbtransitive

   To cause something to rot or deteriorate.

   Salt spray had decayed the pier's wooden pilings.

   Years of neglect decay even the strongest institutions.

   Similarrot, corrode, erode, weaken, undermine

   Note

   With an object, the verb puts the cause up front: humidity decays wooden sculptures, salt spray decays a pier. People and their qualities can be the object too, as in Twelfth Night's "Infirmity, that decays the wise," where weakness wears down wisdom itself rather than wood or stone.

6. 6
   verbintransitive

   Of an unstable atom, to change by fission, by giving off radiation, or by capturing or losing electrons; to undergo radioactive decay.

   Carbon-14 atoms decay at a steady rate, which lets scientists date ancient bones.

   When the nucleus decayed, it released an alpha particle.

   Note

   Physicists describe the change by what an atom gives off or what it turns into: a nucleus decays by alpha or beta emission, or decays to or into a daughter element, as uranium decays to radium through a long chain of steps. How fast an isotope decays is given by its half-life, the time in which half of a sample changes.

7. 7
   nuclear changenouncountable or uncountableabbreviationellipsis

   Ellipsis of radioactive decay.

   Alpha decay releases a helium nucleus and leaves behind a lighter element.

   Heat from decay deep inside the earth helps keep its interior hot.

   Note

   Among physicists the bare noun is enough, since context rules out rot. It is uncountable for the process (the rate of decay) and countable for single events, the decays a detector records, and a word in front usually names the kind: alpha decay, beta decay. For general readers, radioactive decay in full is the safer choice.

8. 8
   electric fadingnoununcountable

   A gradual decrease in a stored electric charge, a magnetic flux, a current, or a similar quantity.

   Engineers measured the decay of current in the coil after the switch was opened.

   Charge decay in the memory cells means the data must be refreshed constantly.

   Similardecrease, decline, loss

9. 9
   sink (orbit)verbintransitive

   Of a satellite's orbit, to lose altitude above the orbited body over a long period.

   Low orbits decay faster than high ones because the air is thicker closer to the ground.

   Engineers expect the probe's orbit to decay within a decade, ending in a fiery reentry.

   Note

   The subject is usually the orbit itself: Skylab, damaged on lift-off, was left up until its orbit decayed. The cause is drag, since even at orbital heights a trace of atmosphere slows a satellite, and each loss of speed lets it sink lower, into thicker air. Hence the periodic boosts a crewed station needs, and the phrase orbital decay for the process.

10. 10
    sink (orbit)noununcountable

    The gradual change in the path of a satellite orbiting Earth, caused by drag from the atmosphere.

    Atmospheric drag produces a steady decay in the orbits of satellites flying low over Earth.

    Mission planners must account for decay when predicting where an old satellite will reenter the atmosphere.

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