coming together vs assemblage

coming together and assemblage both are nouns.

Word	Noun	Adjective	Verb	Adverb
coming together	Yes	No	No	No
assemblage	Yes	No	No	No

As nouns, assemblage is a hypernym of coming together; that is, assemblage is a word with a broader meaning than coming together:

Other hypernyms of coming together include assembly, gathering.

coming together (noun)	assemblage (noun)
the social act of assembling for some common purpose	the social act of assembling
the act of joining together as one	a system of components assembled together for a particular purpose
	a group of persons together in one place
	several things grouped together or considered as a whole