omnium-gatherum vs mixture

omnium-gatherum and mixture both are nouns.

Word	Noun	Adjective	Verb	Adverb
omnium-gatherum	Yes	No	No	No
mixture	Yes	No	No	No

As nouns, mixture is a hypernym of omnium-gatherum; that is, mixture is a word with a broader meaning than omnium-gatherum:

Other hypernyms of omnium-gatherum include assortment, miscellanea, miscellany, mixed bag, motley, potpourri, salmagundi, smorgasbord, variety.

omnium-gatherum (noun)	mixture (noun)
a motley assortment of things	the act of mixing together
	an event that combines things in a mixture
	any foodstuff made by combining different ingredients
	a collection containing a variety of sorts of things
	(chemistry) a substance consisting of two or more substances mixed together (not in fixed proportions and not with chemical bonding)