assumption vs given

assumption and given both are nouns.

Word	Noun	Adjective	Verb	Adverb
assumption	Yes	No	No	No
given	Yes	Yes	No	No

As nouns, given is a hyponym of assumption; that is, given is a word with a more specific, narrower meaning than assumption:

assumption (noun)	given (noun)
the act of taking possession of or power over something	an assumption that is taken for granted
the act of assuming or taking for granted
audacious (even arrogant) behavior that you have no right to
a hypothesis that is taken for granted
a statement that is assumed to be true and from which a conclusion can be drawn

assumption (adjective)	given (adjective)
	acknowledged as a supposition
	(usually followed by `to') naturally disposed toward