brandy vs Cognac

brandy and Cognac both are nouns.

Word	Noun	Adjective	Verb	Adverb
brandy	Yes	No	No	No
Cognac	Yes	No	No	No

As nouns, Cognac is a hyponym of brandy; that is, Cognac is a word with a more specific, narrower meaning than brandy:

brandy: distilled from wine or fermented fruit juice
Cognac: high quality grape brandy distilled in the Cognac district of France

Other hyponyms of brandy include eau de vie, applejack, Calvados, Armagnac, grappa, kirsch, marc, slivovitz.

brandy (noun)	Cognac (noun)
distilled from wine or fermented fruit juice	high quality grape brandy distilled in the Cognac district of France