probable vs prospective

probable

adj
  • Likely to happen. 

  • Supporting, or giving ground for, belief, but not demonstrating. 

  • Likely or most likely to be true. 

noun
  • A person who is likely to appear or do a certain thing. 

  • Something that is likely. 

prospective

adj
  • Likely or expected to happen or become. 

  • Anticipated in the near or far future. 

  • Indicating grammatically an activity about to begin. 

  • Of or relating to a prospect; furnishing a prospect. 

  • Looking forward in time; acting with foresight. 

  • A study that starts with the present situation and follows participants into the future 

noun
  • 1613 March 2 (first performance), Francis Beaumont, “The Masque of the Inner-Temple and Gray’s Inn, Gray’s Inn and the Inner-Temple;[…]”, in The Dramatic Works of Ben Jonson, and Beaumont and Fletcher:[…], volume IV, London: […] John Stockdale,[…], published 1811, →OCLC, page 573, column 2 

  • [T]hey [two pavillions] were trimmed on the inside with rich armour and military furniture, hanged up as upon the walls; and behind the tents there were represented, in prospective, the tops of divers other tents, as if it had been a camp. 

  • A prospective (potential) member, student, employee, date, partner, etc. 

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