indifferent vs monotonic

indifferent

adj
  • Ambivalent; unconcerned; uninterested, apathetic. 

  • Indicating or reflecting a lack of concern or care. 

  • Having no preference. 

  • Mediocre (usually used negatively in modern usage). 

  • Not making a difference; without significance or importance. 

  • Being in the state of neutral equilibrium. 

noun
  • A person who is indifferent or apathetic. 

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. 

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