concomitant vs synchronicity

concomitant

noun
  • Something happening or existing at the same time. 

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

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. 

synchronicity

noun
  • The state of being synchronous or simultaneous. 

  • Coincidences that seem to be meaningfully related; supposedly the result of "universal forces". 

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