concomitant vs occurrence

concomitant and occurrence both are nouns.

Word	Noun	Adjective	Verb	Adverb
concomitant	Yes	Yes	No	No
occurrence	Yes	No	No	No

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

concomitant: an event or situation that happens at the same time as or in connection with another
occurrence: an event that happens

Other hypernyms of concomitant include happening, natural event, occurrent.

concomitant (noun)	occurrence (noun)
an event or situation that happens at the same time as or in connection with another	an event that happens
	an instance of something occurring

concomitant (adjective)	occurrence (adjective)
occurring with or following as a consequence