discontinuity vs progression

discontinuity

noun
  • a subterranean interface at which seismic velocities change 

  • A lack of continuity, regularity or sequence; a break or gap. 

  • A point in the range of a function at which it is undefined or discontinuous. 

progression

noun
  • A sequence obtained by adding or multiplying each term by a constant. 

  • chord progression 

  • The act of moving from one thing to another. 

  • The act of moving forward or proceeding in a course; motion onward. 

  • Development, increase, evolution. 

  • The making an exercise more exerting by manipulating the details of its performance like loaded weight, range of motion, angle, speed. 

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