gap vs improvement

gap

verb
  • To leave suddenly. 

  • To notch, as a sword or knife. 

  • To check the size of a gap. 

  • To make an opening in; to breach. 

noun
  • A vacancy, deficit, absence, or lack. 

  • The shortfall between the amount the medical insurer will pay to the service provider and the scheduled fee for the item. 

  • An opening in anything made by breaking or parting. 

  • A hiatus, a pause in something which is otherwise continuous. 

  • An opening allowing passage or entrance. 

  • An opening that implies a breach or defect. 

  • (usually written as "the gap") The disparity between the indigenous and non-indigenous communities with regard to life expectancy, education, health, etc. 

  • An unsequenced region in a sequence alignment. 

  • The regions between the outfielders. 

  • A vacant space or time. 

  • A mountain or hill pass. 

  • A sheltered area of coast between two cliffs (mostly restricted to place names). 

improvement

noun
  • 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 

  • 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. 

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