emperor vs sovereign

emperor and sovereign both are nouns.

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

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

Other hypernyms of emperor include crowned head, monarch.

emperor (noun)	sovereign (noun)
large richly colored butterfly	a nation's ruler or head of state usually by hereditary right
large moth of temperate forests of Eurasia having heavily scaled transparent wings
red table grape of California
the male ruler of an empire

emperor (adjective)	sovereign (adjective)
	greatest in status or authority or power
	(of political bodies) not controlled by outside forces