shell bean vs fava bean

shell bean and fava bean both are nouns.

Word	Noun	Adjective	Verb	Adverb
shell bean	Yes	No	No	No
fava bean	Yes	No	No	No

As nouns, fava bean is a hyponym of shell bean; that is, fava bean is a word with a more specific, narrower meaning than shell bean:

Other hyponyms of shell bean include lima bean, butter bean, butterbean, civet bean, sieva bean, broad bean, green soybean.

shell bean (noun)	fava bean (noun)
unripe beans removed from the pod before cooking	shell beans cooked as lima beans
a bean plant grown primarily for its edible seed rather than its pod	seed of the broad-bean plant