head cabbage vs savoy

head cabbage and savoy both are nouns.

Word	Noun	Adjective	Verb	Adverb
head cabbage	Yes	No	No	No
savoy	Yes	No	No	No

As nouns, savoy is a hyponym of head cabbage; that is, savoy is a word with a more specific, narrower meaning than head cabbage:

head cabbage: any of several varieties of cabbage having a large compact globular head; may be steamed or boiled or stir-fried or used raw in coleslaw
savoy: head of soft crinkly leaves

Other hyponyms of head cabbage include red cabbage, savoy cabbage.

head cabbage (noun)	savoy (noun)
any of several varieties of cabbage having a large compact globular head; may be steamed or boiled or stir-fried or used raw in coleslaw	head of soft crinkly leaves
any of various cultivated cabbage plants having a short thick stalk and large compact head of edible usually green leaves