decenary vs decennial

decenary

adj
  • Of or related to the number ten, (particularly) as a base of numeration. 

  • Of or related to a tithing. 

  • Containing or comprising ten items or units. 

noun
  • A tithing. 

decennial

adj
  • Of or related to a ten-year period, as a term of office. 

  • Occurring every ten years. 

noun
  • The tenth anniversary of an event or happening. 

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