conjuncture vs copula

conjuncture

noun
  • A combination of events or circumstances; a conjunction; a union. 

  • A set of circumstances causing a crisis; a juncture. 

copula

noun
  • A word, usually a verb, used to link the subject of a sentence with a predicate (usually a subject complement or an adverbial), that unites or associates the subject with the predicate. 

  • A device that connects two or more keyboards of an organ. 

  • A function that represents the association between two or more variables, independent of the individual marginal distributions of the variables. 

  • The act of copulation; mating. 

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