abortus vs foetus

abortus and foetus both are nouns.

Word	Noun	Adjective	Verb	Adverb
abortus	Yes	No	No	No
foetus	Yes	No	No	No

As nouns, foetus is a hypernym of abortus; that is, foetus is a word with a broader meaning than abortus:

abortus: a human fetus whose weight is less than 0.5 kilogram when removed or expelled from the mother's body
foetus: an unborn or unhatched vertebrate in the later stages of development showing the main recognizable features of the mature animal

Other hypernyms of abortus include fetus.

abortus (noun)	foetus (noun)
a human fetus whose weight is less than 0.5 kilogram when removed or expelled from the mother's body	an unborn or unhatched vertebrate in the later stages of development showing the main recognizable features of the mature animal