quotation vs epigraph

quotation and epigraph both are nouns.

Word	Noun	Adjective	Verb	Adverb
quotation	Yes	No	No	No
epigraph	Yes	No	No	No

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

Other hyponyms of quotation include mimesis, misquotation, misquote, agraphon.

quotation (noun)	epigraph (noun)
the practice of quoting from books or plays etc.	an engraved inscription
a passage or expression that is quoted or cited	a quotation at the beginning of some piece of writing
a short note recognizing a source of information or of a quoted passage
a statement of the current market price of a security or commodity