co-occurrence vs simultaneity

co-occurrence and simultaneity both are nouns.

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

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

co-occurrence: the temporal property of two things happening at the same time
simultaneity: happening or existing or done at the same time

Other hypernyms of co-occurrence include simultaneousness.

co-occurrence (noun)	simultaneity (noun)
the temporal property of two things happening at the same time	happening or existing or done at the same time
an event or situation that happens at the same time as or in connection with another