posthumous birth vs nativity

posthumous birth and nativity both are nouns.

Word	Noun	Adjective	Verb	Adverb
posthumous birth	Yes	No	No	No
nativity	Yes	No	No	No

As nouns, nativity is a hypernym of posthumous birth; that is, nativity is a word with a broader meaning than posthumous birth:

posthumous birth: birth of a child by Caesarean section after the death of the mother
nativity: the event of being born

Other hypernyms of posthumous birth include birth, nascence, nascency.

As nouns, nativity is a hypernym of posthumous birth; that is, nativity is a word with a broader meaning than posthumous birth:

Other hypernyms of posthumous birth include birth, nascence, nascency.

posthumous birth (noun)	nativity (noun)
birth of a child by Caesarean section after the death of the mother	the event of being born
birth of a child after the father has died