comprehensible vs unclear

comprehensible

adj
  • Able to be comprehended. 

unclear

adj
  • Not easy to see or read; indecipherable or unreadable. 

  • Ambiguous; liable to more than one interpretation. 

  • Not having a clear idea; uncertain. 

  • Not clearly or explicitly defined. 

verb
  • To undo the process of clearing. 

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