unevenness vs variability

unevenness

noun
  • The result or product of being uneven. 

  • A rough or uneven thing. 

  • The quality or characteristic of being uneven; irregularity; inconsistency; the lack of smoothness or continuity. 

variability

noun
  • The state or characteristic of being variable. 

  • The degree to which a thing is variable. In data or statistics this is often a measurement of distance from the mean or a description of data range. 

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