empress vs emperor

empress and emperor both are nouns.

Word	Noun	Adjective	Verb	Adverb
empress	Yes	No	No	No
emperor	Yes	No	No	No

As nouns, emperor is a hypernym of empress; that is, emperor is a word with a broader meaning than empress:

Other hypernyms of empress include adult female, woman.

empress (noun)	emperor (noun)
a woman emperor or the wife of an emperor	large richly colored butterfly
	large moth of temperate forests of Eurasia having heavily scaled transparent wings
	red table grape of California
	the male ruler of an empire