Merlot vs vinifera grape

Merlot and vinifera grape both are nouns.

Word	Noun	Adjective	Verb	Adverb
Merlot	Yes	No	No	No
vinifera grape	Yes	No	No	No

As nouns, vinifera grape is a hypernym of Merlot; that is, vinifera grape is a word with a broader meaning than Merlot:

Merlot: black wine grape originally from the region of Bordeaux
vinifera grape: common European grape cultivated in many varieties; chief source of Old World wine and table grapes

Other hypernyms of Merlot include common grape vine, vinifera, Vitis vinifera.

Merlot (noun)	vinifera grape (noun)
dry red wine made from a grape grown widely in Bordeaux and California	grape from a cultivated variety of the common grape vine of Europe
black wine grape originally from the region of Bordeaux	common European grape cultivated in many varieties; chief source of Old World wine and table grapes