tenno vs emperor

tenno and emperor both are nouns.

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

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

tenno: the emperor of Japan; when regarded as a religious leader the emperor is called tenno
emperor: the male ruler of an empire

tenno (noun)	emperor (noun)
the emperor of Japan; when regarded as a religious leader the emperor is called tenno	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