alumnus vs postgraduate

alumnus

noun
  • A male graduate. 

  • A student of any gender. 

  • A male pupil or student. 

  • A graduate of any gender. 

postgraduate

noun
  • A person continuing to study in a field after having successfully completed a degree course. 

adj
  • Of studies which take place after having successfully completed a degree course. 

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