given vs assumption

given and assumption both are nouns.

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

As nouns, assumption is a hypernym of given; that is, assumption is a word with a broader meaning than given:

Other hypernyms of given include supposal, supposition.

given (noun)	assumption (noun)
an assumption that is taken for granted	the act of taking possession of or power over something
	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

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