caviar vs roe

caviar and roe both are nouns.

Word	Noun	Adjective	Verb	Adverb
caviar	Yes	No	No	No
roe	Yes	No	No	No

As nouns, roe is a hypernym of caviar; that is, roe is a word with a broader meaning than caviar:

caviar: salted roe of sturgeon or other large fish; usually served as an hors d'oeuvre
roe: fish eggs or egg-filled ovary; having a grainy texture

Other hypernyms of caviar include hard roe.

caviar (noun)	roe (noun)
salted roe of sturgeon or other large fish; usually served as an hors d'oeuvre	eggs of female fish
	the eggs or egg-laden ovary of a fish
	the egg mass or spawn of certain crustaceans such as the lobster
	fish eggs or egg-filled ovary; having a grainy texture