concomitance vs concurrence

concomitance and concurrence both are nouns.

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

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

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

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

concomitance (noun)	concurrence (noun)
occurrence or existence together or in connection with one another	acting together, as agents or circumstances or events
	the temporal property of two things happening at the same time
	agreement of results or opinions
	a state of cooperation