emperor vs crowned head

emperor and crowned head both are nouns.

Word	Noun	Adjective	Verb	Adverb
emperor	Yes	No	No	No
crowned head	Yes	No	No	No

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

Other hypernyms of emperor include monarch, sovereign.

emperor (noun)	crowned head (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