tomb vs burial chamber

tomb and burial chamber both are nouns.

Word	Noun	Adjective	Verb	Adverb
tomb	Yes	No	No	No
burial chamber	Yes	No	No	No

As nouns, burial chamber is a hyponym of tomb; that is, burial chamber is a word with a more specific, narrower meaning than tomb:

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

Other hyponyms of tomb include sepulcher, sepulchre, sepulture, mastaba, mastabah.

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