conjunction vs simultaneousness

conjunction and simultaneousness both are nouns.

Word	Noun	Adjective	Verb	Adverb
conjunction	Yes	No	No	No
simultaneousness	Yes	No	No	No

As nouns, simultaneousness is a hypernym of conjunction; that is, simultaneousness is a word with a broader meaning than conjunction:

Other hypernyms of conjunction include simultaneity.

conjunction (noun)	simultaneousness (noun)
something that joins or connects	happening or existing or done at the same time
the temporal property of two things happening at the same time
an uninflected function word that serves to conjoin words or phrases or clauses or sentences
(astronomy) apparent meeting or passing of two or more celestial bodies in the same degree of the zodiac
the grammatical relation between linguistic units (words or phrases or clauses) that are connected by a conjunction
the state of being joined together