decay vs rate

decay

verb
  • To rot, to go bad. 

  • 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 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. 

rate

verb
  • To berate, scold. 

  • To ascertain the exact rate of the gain or loss of (a chronometer) as compared with true time. 

  • To assign or be assigned a particular rank or level. 

  • To evaluate a property's value for the purposes of local taxation. 

  • To evaluate or estimate the value of. 

  • To have position (in a certain class). 

  • To deserve; to be worth. 

  • To have value or standing. 

  • To determine the limits of safe functioning for a machine or electrical device. 

  • To consider or regard. 

  • To like; to think highly of. 

  • To ratify. 

noun
  • A class into which ships were assigned based on condition, size etc.; by extension, rank. 

  • The price of (an individual) thing; cost. 

  • The gain or loss of a timepiece in a unit of time. 

  • The relative speed of change or progress. 

  • The proportional relationship between one amount, value etc. and another. 

  • A set price or charge for all examples of a given case, commodity, service etc. 

  • A wage calculated in relation to a unit of time. 

  • Any of various taxes, especially those levied by a local authority. 

  • Speed. 

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