dubious vs monotone

dubious

adj
  • Generally considered imprecise or wrong, but not totally unplayable. 

  • Arousing doubt; questionable; open to suspicion. 

  • In disbelief; wavering, uncertain, or hesitating in opinion; inclined to doubt; undecided. 

monotone

adj
  • Being, or having the salient properties of, a monotone function. 

  • Having a single unvaried pitch. 

verb
  • To speak in a monotone. 

noun
  • A piece of writing in one strain throughout. 

  • A single unvaried tone of speech or a sound. 

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