erratic vs inconsistent

erratic

adj
  • Deviating from normal opinions or actions; eccentric; odd. 

  • Unsteady, random; prone to unexpected changes; not consistent. 

noun
  • A rock moved from one location to another, usually by a glacier. 

  • Anything that has erratic characteristics. 

inconsistent

adj
  • Not consistent or coherent in thought or behavior. 

  • Lacking internal consistency; self-contradicting; not compatible with itself. 

  • Having the property that a contradiction can be derived. 

  • Not compatible (with another thing); incompatible, discrepant, at odds. 

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