navel orange vs sweet orange

navel orange and sweet orange both are nouns.

Word	Noun	Adjective	Verb	Adverb
navel orange	Yes	No	No	No
sweet orange	Yes	No	No	No

As nouns, sweet orange is a hypernym of navel orange; that is, sweet orange is a word with a broader meaning than navel orange:

navel orange (noun)	sweet orange (noun)
seedless orange enclosing a small secondary fruit at the apex	orange with sweet juicy pulp; often has a thin skin
	probably native to southern China; widely cultivated as source of table and juice oranges