sepulcher vs monument

sepulcher and monument both are nouns.

Word	Noun	Adjective	Verb	Adverb
sepulcher	Yes	No	No	No
monument	Yes	No	No	No

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

Other hyponyms of sepulcher include crypt, mausoleum, repository, burial vault, vault.

sepulcher (noun)	monument (noun)
a chamber that is used as a grave	a structure erected to commemorate persons or events
	a burial vault (usually for some famous person)
	an important site that is marked and preserved as public property