improvement vs refinement

improvement

noun
  • The act of making profitable use or application of anything, or the state of being profitably employed; practical application, for example of a doctrine, principle, or theory, stated in a discourse. 

  • Increase; growth; progress; advance. 

  • The act of improving; advancement or growth; a bettering 

  • Something which is improved 

  • Valuable additions or betterments, for example buildings, clearings, drains, fences, etc., on premises. 

  • A useful addition to, or modification of, a machine, manufacture, or composition. 

  • The state of being improved; betterment; advance 

refinement

noun
  • The act, or the result of refining; the removal of impurities, or a purified material 

  • A fine or subtle distinction. 

  • High-class style; cultivation. 

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