pertinency vs relativity

pertinency

noun
  • The quality of being pertinent to the matter at hand; relevance. 

relativity

noun
  • The state of being relative to something else; the absence of universally applicable rules or standards; relativism; (countable) an instance of this. 

  • Also Einsteinian relativity: the reliance of the nature of physical phenomena (such as gravity, light, mass, and time) on the relative motion between an observer and the thing observed, as developed by Albert Einstein in two theories, special relativity and general relativity. 

  • The difference in pay or positions between different employees in a business (internal relativity), or between different businesses (external relativity); a differential. 

  • An evaluation of the similarities and differences between things; a comparison; hence, a difference in position or status between things; a disparity. 

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