concomitance vs co-occurrence

concomitance and co-occurrence both are nouns.

Word	Noun	Adjective	Verb	Adverb
concomitance	Yes	No	No	No
co-occurrence	Yes	No	No	No

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

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

Other hypernyms of concomitance include coincidence, concurrence, conjunction.

concomitance (noun)	co-occurrence (noun)
occurrence or existence together or in connection with one another	the temporal property of two things happening at the same time
	an event or situation that happens at the same time as or in connection with another