fluctuation vs variation

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. 

variation

noun
  • The angular difference at the vessel between the direction of true north and magnetic north. 

  • Deviation from the mean orbit of a heavenly body. 

  • The act of varying; a partial change in the form, position, state, or qualities of a thing. 

  • A related but distinct thing. 

  • A line of play that differs from the original. 

  • The modification of a hereditary trait. 

  • A technique where material is repeated with alterations to the melody, harmony, rhythm, timbre, texture, counterpoint or orchestration; but with some invariant characteristic, e.g. a ground bass. 

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