Rhine wine vs Riesling

Rhine wine and Riesling both are nouns.

Word	Noun	Adjective	Verb	Adverb
Rhine wine	Yes	No	No	No
Riesling	Yes	No	No	No

As nouns, Riesling is a hyponym of Rhine wine; that is, Riesling is a word with a more specific, narrower meaning than Rhine wine:

Rhine wine: any of several white wines from the Rhine River valley in Germany (`hock' is British usage)
Riesling: fragrant dry or sweet white wine from the Rhine valley or a similar wine from California

Other hyponyms of Rhine wine include liebfraumilch.

Rhine wine (noun)	Riesling (noun)
any of several white wines from the Rhine River valley in Germany (`hock' is British usage)	fragrant dry or sweet white wine from the Rhine valley or a similar wine from California
	white grape grown in Europe and California