amateur vs semi-professional

amateur

noun
  • Someone who is unqualified or insufficiently skillful. 

  • A person attached to a particular pursuit, study, science, or art (such as music or painting), especially one who cultivates any study, interest, taste, or attachment without engaging in it professionally. 

adj
  • Showing a lack of professionalism, experience or talent. 

  • Non-professional. 

  • Created, done, or populated by amateurs or non-professionals. 

semi-professional

noun
  • a semi-professional sportsman or athlete 

adj
  • playing for pay on a part-time basis 

  • composed of semi-professional players 

How often have the words amateur and semi-professional occurred in a corpus of books? (source: Google Ngram Viewer )