murderess vs murderer

murderess and murderer both are nouns.

Word	Noun	Adjective	Verb	Adverb
murderess	Yes	No	No	No
murderer	Yes	No	No	No

As nouns, murderer is a hypernym of murderess; that is, murderer is a word with a broader meaning than murderess:

murderess: a woman murderer
murderer: a criminal who commits homicide (who performs the unlawful premeditated killing of another human being)

Other hypernyms of murderess include liquidator, manslayer, adult female, woman.

murderess (noun)	murderer (noun)
a woman murderer	a criminal who commits homicide (who performs the unlawful premeditated killing of another human being)