discontinuity vs severance

discontinuity

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

  • a subterranean interface at which seismic velocities change 

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

severance

noun
  • A separation. 

  • The act of severing or the state of being severed. 

  • A severance payment. 

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