decay vs fade

decay

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

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

  • 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). 

noun
  • The process or result of being gradually decomposed. 

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

  • 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. 

fade

verb
  • To grow weak; to lose strength; to decay; to perish gradually; to wither, as a plant. 

  • To hit the ball with the shot called a fade. 

  • To bet against. 

  • To lose freshness, color, or brightness; to become faint in hue or tint; hence, to be wanting in color. 

  • To sink away; to disappear gradually; to grow dim; to vanish. 

  • To cause to fade. 

noun
  • A haircut where the hair is short or shaved on the sides of the head and longer on top. See also high-top fade and low fade. 

  • The act of disappearing from a place so as not to be found; covert departure. 

  • A golf shot that curves intentionally to the player's right (if they are right-handed) or to the left (if left-handed). 

  • A fight. 

  • A gradual decrease in the brightness of a shot or the volume of sound or music (as a means of cutting to a new scene or starting a new song). 

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