monotonic vs unvaried

monotonic

adj
  • Uttered in a monotone; monotonous. 

  • said of a function that either never decreases or never increases as its independent variable increases. 

  • of or using the Greek system of diacritics which discards the breathings and employs a single accent to indicate stress. It replaced polytonic system in 1982. 

unvaried

adj
  • not varied; monotonous or homogeneous; samely 

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