learn vs retain

learn

verb
  • To acquire, or attempt to acquire knowledge or an ability to do something. 

  • To attend a course or other educational activity. 

  • To teach. 

  • To come to know; to become informed of; to find out. 

  • To gain knowledge from a bad experience so as to improve. 

  • To study. 

noun
  • The act of learning something 

retain

verb
  • To keep in possession or use. 

  • To employ by paying a retainer. 

  • To hold back (a pupil) instead of allowing them to advance to the next class or year. 

  • To keep in one's pay or service. 

  • To hold secure. 

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