mastaba vs tomb

mastaba and tomb both are nouns.

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

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

mastaba: an ancient Egyptian mud-brick tomb with a rectangular base and sloping sides and flat roof
tomb: a place for the burial of a corpse (especially beneath the ground and marked by a tombstone)

Other hypernyms of mastaba include grave.

mastaba (noun)	tomb (noun)
an ancient Egyptian mud-brick tomb with a rectangular base and sloping sides and flat roof	a place for the burial of a corpse (especially beneath the ground and marked by a tombstone)