fundamental vs unbelief

fundamental

noun
  • The lowest frequency of a periodic waveform. 

  • A main or major principle, rule, law, etc. which serves as the foundation or basis of a system; an essential part 

  • The lowest partial of a complex tone. 

adj
  • Related to a foundation. base, or basis; serving as a foundation. 

  • essential; extremely important 

unbelief

noun
  • An absence (or rejection) of belief, especially religious belief 

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