monument vs sepulcher

monument and sepulcher both are nouns.

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

As nouns, sepulcher is a hypernym of monument; that is, sepulcher is a word with a broader meaning than monument:

Other hypernyms of monument include burial chamber, sepulchre, sepulture.

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