partial abortion vs stillbirth

partial abortion and stillbirth both are nouns.

Word	Noun	Adjective	Verb	Adverb
partial abortion	Yes	No	No	No
stillbirth	Yes	No	No	No

As nouns, stillbirth is a hypernym of partial abortion; that is, stillbirth is a word with a broader meaning than partial abortion:

partial abortion: termination of pregnancy without expulsion of all of the products of conception
stillbirth: a natural loss of the products of conception

Other hypernyms of partial abortion include miscarriage, spontaneous abortion.

partial abortion (noun)	stillbirth (noun)
termination of pregnancy without expulsion of all of the products of conception	a natural loss of the products of conception