exclusion vs introduction

exclusion

noun
  • The act of excluding or shutting out; removal from consideration or taking part. 

  • An item not covered by an insurance policy. 

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 exclusion and introduction occurred in a corpus of books? (source: Google Ngram Viewer )