difference vs observance

difference

noun
  • A disagreement or argument. 

  • The result of a subtraction; sometimes the absolute value of this result. 

  • An addition to a coat of arms to distinguish two people's bearings which would otherwise be the same. See augmentation and cadency. 

  • A characteristic of something that makes it different from something else. 

  • The quality of being different. 

  • The quality or attribute which is added to those of the genus to constitute a species; a differentia. 

  • The set of elements that are in one set but not another ( scriptstyle A◌̅B). 

  • Significant change in or effect on a situation or state. 

  • A Boolean operation which is true when the two input variables are different but is otherwise false; the XOR operation ( scriptstyle A◌̅B+◌̅AB). 

observance

noun
  • Observation or the act of watching. 

  • The practice of complying with a law, custom, command or rule. 

  • That which is to be observed. 

  • A rule governing a religious order, especially in the Roman Catholic church. 

  • The custom of celebrating a holiday or similar occasion. 

  • Reverence; homage. 

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