discourse vs headword

discourse

noun
  • Expression in words, either speech or writing. 

  • A formal lengthy exposition of some subject, either spoken or written. 

  • An institutionalized way of thinking, a social boundary defining what can be said about a specific topic (after Michel Foucault). 

  • Any rational expression, reason. 

verb
  • To exercise reason; to employ the mind in judging and inferring; to reason. 

  • To engage in discussion or conversation; to converse. 

  • To write or speak formally and at length. 

headword

noun
  • Any word which may be modified by an adjunct. 

  • A word used as the title of a section, particularly in a dictionary, encyclopedia, or thesaurus. 

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