concomitance vs coincidence

concomitance and coincidence both are nouns.

Word	Noun	Adjective	Verb	Adverb
concomitance	Yes	No	No	No
coincidence	Yes	No	No	No

As nouns, coincidence is a hypernym of concomitance; that is, coincidence is a word with a broader meaning than concomitance:

concomitance: occurrence or existence together or in connection with one another
coincidence: the temporal property of two things happening at the same time

Other hypernyms of concomitance include co-occurrence, concurrence, conjunction.

concomitance (noun)	coincidence (noun)
occurrence or existence together or in connection with one another	the temporal property of two things happening at the same time
	the quality of occupying the same position or area in space
	an event that might have been arranged although it was really accidental