addendum vs expansion

addendum

noun
  • Something to be added; especially text added as an appendix or supplement to a document. 

  • The height by which the tooth of a gear projects beyond (outside for external, or inside for internal) the standard pitch circle or pitch line. 

  • A postscript. 

expansion

noun
  • A new addition. 

  • A product to be used with a previous product. 

  • That which is expanded; expanse; extended surface. 

  • The operation of steam in a cylinder after its communication with the boiler has been cut off, by which it continues to exert pressure upon the moving piston. 

  • The replacement of a short name (e.g., acronym, initialism, alphanumeric symbol, abbreviation) with the longer name that is synonymous with it, as when spelling out acronyms to ensure clarity for a general audience. 

  • The string of text thus substituted. 

  • An act, process, or instance of expanding. 

  • The fractional change in unit length per unit length per unit temperature change. 

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