apostrophe vs digression

apostrophe

noun
  • A sudden exclamatory piece of dialogue addressed to someone or something, especially absent. 

  • The text character ’, which serves as a punctuation mark in various languages and as a diacritical mark in certain rare contexts. 

digression

noun
  • An aside, an act of straying from the main subject in speech or writing. 

  • The act of straying from the main subject in speech or writing, (rhetoric) particularly for rhetorical effect. 

  • An elongation, a deflection or deviation from a mean position or expected path. 

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