paperback vs recto

paperback

noun
  • A book with flexible binding. 

adj
  • Having flexible binding. 

verb
  • To issue or publish (a book) in a paperback edition. 

recto

noun
  • The right-hand page of a book of a script which reads from left to right, usually having an odd page number. 

  • A writ of right. 

  • The front side of a flat object which is to be examined visually, as for reading, such as a sheet, leaf, coin or medal. 

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