ancestress vs ancestor

ancestress and ancestor both are nouns.

Word	Noun	Adjective	Verb	Adverb
ancestress	Yes	No	No	No
ancestor	Yes	No	No	No

As nouns, ancestor is a hypernym of ancestress; that is, ancestor is a word with a broader meaning than ancestress:

ancestress: a woman ancestor
ancestor: someone from whom you are descended (but usually more remote than a grandparent)

Other hypernyms of ancestress include antecedent, ascendant, ascendent, root.

ancestress (noun)	ancestor (noun)
a woman ancestor	someone from whom you are descended (but usually more remote than a grandparent)