forerunner vs predecessor

forerunner

noun
  • A forebear, an ancestor, a predecessor. 

  • By extension, a non-competitor who leads out the competitors on to the circuit, or who runs/rides the course prior to competitor trials, usually testing or checking the way. 

  • A postage stamp used in the time before a region or area issues stamps of its own. 

  • A runner at the front or ahead. 

  • A precursor or harbinger, a warning ahead. 

predecessor

noun
  • One who precedes; one who has preceded another in any state, position, office, etc.; one whom another follows or comes after, in any office or position. 

  • A model or type of machinery or device which precedes the current (or later) one. Usually used to describe an earlier, outdated model. 

  • A vertex having a directed path to another vertex 

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