continuative vs invariable

continuative

adj
  • Of or pertaining to continuation. 

  • durative. 

noun
  • a durative. 

  • Something that causes a continuation. 

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 continuative and invariable occurred in a corpus of books? (source: Google Ngram Viewer )