calf vs box calf

calf and box calf both are nouns.

Word	Noun	Adjective	Verb	Adverb
calf	Yes	No	No	No
box calf	Yes	No	No	No

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

calf (noun)	box calf (noun)
young of domestic cattle	black calfskin leather tanned with chromium salts
young of various large placental mammals e.g. whale or giraffe or elephant or buffalo
the muscular back part of the shank
fine leather from the skin of a calf