addition vs introduction

addition

noun
  • The act of adding anything. 

  • The arithmetic operation of adding. 

  • A dot at the right side of a note as an indication that its sound is to be lengthened one half. 

  • Anything that is added. 

  • A title annexed to a person's name to identify him or her more precisely. 

  • Something added to a coat of arms, as a mark of honour. 

introduction

noun
  • The act or process of introducing. 

  • A written or oral explanation of what constitutes the basis of an issue. 

  • A means, such as a personal letter, of presenting one person to another. 

  • An initial section of a book or article, which introduces the subject material. 

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