decay vs fail

decay

noun
  • A deterioration of condition; loss of status or fortune. 

  • The process or result of being gradually decomposed. 

  • The situation, in programming languages such as C, where an array loses its type and dimensions and is reduced to a pointer, for example by passing it to a function. 

verb
  • To undergo bit rot, that is, gradual degradation. 

  • To deteriorate, to get worse, to lose strength or health, to decline in quality. 

  • To undergo optical decay, that is, to relax to a less excited state, usually by emitting a photon or phonon. 

  • Loss of airspeed due to drag. 

  • To undergo software rot, that is, to fail to be updated in a changing environment, so as to eventually become legacy or obsolete. 

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

  • To cause to rot or deteriorate. 

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

  • To rot, to go bad. 

  • To undergo prolonged reduction in altitude (above the orbited body). 

fail

noun
  • A failure (something incapable of success). 

  • A failure, especially of a financial transaction (a termination of an action). 

  • A failure (condition of being unsuccessful). 

  • A failing grade in an academic examination. 

  • Poor quality; substandard workmanship. 

  • A piece of turf cut from grassland. 

adj
  • Unsuccessful; inadequate; unacceptable in some way. 

verb
  • Not to achieve a particular stated goal. (Usage note: The direct object of this word is usually an infinitive.) 

  • To become unable to meet one's engagements; especially, to be unable to pay one's debts or discharge one's business obligation; to become bankrupt or insolvent. 

  • To receive one or more non-passing grades in academic pursuits. 

  • To give a student a non-passing grade in an academic endeavour. 

  • To be wanting to, to be insufficient for, to disappoint, to desert; to disappoint one's expectations. 

  • To be wanting; to fall short; to be or become deficient in any measure or degree up to total absence. 

  • To neglect. 

  • To be unsuccessful. 

  • Of a machine, etc.: to cease to operate correctly. 

How often have the words decay and fail occurred in a corpus of books? (source: Google Ngram Viewer )