continuant vs invariable

continuant

adj
  • Continuing; prolonged; sustained. 

noun
  • An endurant. 

  • A determinant formed from a tridiagonal matrix. 

  • A linguistic sound other than a stop. 

invariable

adj
  • Constant. 

  • Not variable; unalterable; uniform; always having the same value. 

  • That cannot undergo inflection, conjugation or declension. 

noun
  • Something that does not vary; a constant. 

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