concomitant vs nonsynchronous

concomitant

noun
  • An invariant homogeneous polynomial in the coefficients of a form, a covariant variable, and a contravariant variable. 

  • Something happening or existing at the same time. 

adj
  • Of or relating to the grammatical aspect which expresses that a secondary action is occurring simultaneously to the primary action of the statement. 

  • Accompanying; conjoining; attending; concurrent. 

nonsynchronous

adj
  • Not synchronous 

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