big vs epic

big is not a noun while epic is a noun.

Word	Noun	Adjective	Verb	Adverb
big	No	Yes	No	Yes
epic	Yes	Yes	No	No

big (noun)	epic (noun)
	a long narrative poem telling of a hero's deeds

big (adjective)	epic (adjective)
above average in size or number or quantity or magnitude or extent	constituting or having to do with or suggestive of a literary epic
conspicuous in position or importance	very imposing or impressive; surpassing the ordinary (especially in size or scale)
given or giving freely
generous and understanding and tolerant
marked by intense physical force
significant
prodigious
serious or severe
loud and firm
(of animals) fully developed
in an advanced stage of pregnancy
feeling self-importance
exhibiting self-importance