alteration vs fluctuation

alteration

noun
  • The state of being altered; a change made in the form or nature of a thing; a changed condition. 

  • The act of altering or making different. 

fluctuation

noun
  • A motion like that of waves; a moving in this and that direction. 

  • A wavering; unsteadiness. 

  • In medicine, a wave-like motion or undulation of a fluid in a natural or abnormal cavity (e.g. pus in an abscess), which is felt during palpation or percussion. 

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