ardency vs ardor

ardency

noun
  • Intensity of heat or burning. 

  • Intensity of devotion. 

  • Intensity of light. 

  • Intensity of feelings. 

ardor

noun
  • Intense heat. 

  • Great warmth of feeling; fervor; passion. 

  • Spirit; enthusiasm; passion. 

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