really vs very

really is not an adjective while very is an adjective.

Word	Noun	Adjective	Verb	Adverb
really	No	No	No	Yes
very	No	Yes	No	Yes

As adverbs, really and very are synonyms defined as:

Other synonyms of really include rattling, real.

really (adjective)	very (adjective)
	precisely as stated
	being the exact same one; not any other:

really (adverb)	very (adverb)
used to give emphasis	used to give emphasis
in fact (used as intensifiers or sentence modifiers)	precisely so
in accordance with truth or fact or reality
in actual fact