preface vs sequel

preface

verb
  • To give a preface to. 

  • To introduce or make a comment before (the main point). 

noun
  • An introduction, or series of preliminary remarks. 

  • A title or epithet. 

  • The beginning or introductory portion that comes before the main text of a document or book. 

  • The prelude or introduction to the canon of the Mass. 

sequel

noun
  • A narrative that is written after another narrative set in the same universe, especially a narrative that is chronologically set after its predecessors, or (perhaps improper usage) any narrative that has a preceding narrative of its own. 

  • The remainder of the text; what follows. Used exclusively in the set phrase "in the sequel". 

  • Thirlage. 

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