sepulchre vs tomb

sepulchre and tomb both are nouns.

Word	Noun	Adjective	Verb	Adverb
sepulchre	Yes	No	No	No
tomb	Yes	No	No	No

As nouns, tomb is a hypernym of sepulchre; that is, tomb is a word with a broader meaning than sepulchre:

sepulchre: a chamber that is used as a grave
tomb: a place for the burial of a corpse (especially beneath the ground and marked by a tombstone)

Other hypernyms of sepulchre include chamber, grave.

sepulchre (noun)	tomb (noun)
a chamber that is used as a grave	a place for the burial of a corpse (especially beneath the ground and marked by a tombstone)