coherence vs obscurity

coherence

noun
  • The property of having the same wavelength and phase. 

  • A logical arrangement of parts, as in writing. 

  • A semantic relationship between different parts of the same text. 

  • The quality of cohering, or being coherent; internal consistency. 

  • The quality of forming a unified whole. 

obscurity

noun
  • The state of being unknown; a thing that is unknown. 

  • The quality of being difficult to understand; a thing that is difficult to understand. 

  • Darkness; the absence of light. 

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