retrofit vs upgrade

retrofit

noun
  • A change made to a device, structure, etc., by introducing components or parts that were not previously available or installed. 

  • An act of supplying a device, structure, etc., with new components or parts that were not previously available or installed; a retrofitting. 

verb
  • To supply (a device, structure, etc.) with new components or parts that were not previously available or installed; to modernize. 

  • Synonym of backport (“to retroactively supply a fix or feature to a previous version of a software product at the same time or after supplying it to the current version.”) 

  • To give new characteristics or make alterations (to someone or something) to suit them to changed circumstances. 

  • To supply a device, structure, etc., with new components or parts that were not previously available or installed. 

  • To add or substitute (new components or parts) that were not previously available for or installed in a device, structure, etc. 

upgrade

noun
  • An improved component or replacement item, usually applied to technology 

  • An upward grade or slope. 

  • An improvement 

verb
  • To improve, usually applied to technology, generally by complete replacement of one or more components 

  • To replace with something better. 

  • To improve the equipment or furnishings of or services rendered to 

  • To replace a program with a later version of itself, a version having a higher version number or marketed under a more recent product name. 

  • To improve in condition or status. 

adv
  • Up a slope or grade. 

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