broad bean vs shell bean plant

broad bean and shell bean plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
broad bean	Yes	No	No	No
shell bean plant	Yes	No	No	No

As nouns, shell bean plant is a hypernym of broad bean; that is, shell bean plant is a word with a broader meaning than broad bean:

broad bean: Old World upright plant grown especially for its large flat edible seeds but also as fodder
shell bean plant: a bean plant grown primarily for its edible seed rather than its pod

Other hypernyms of broad bean include shell bean.

broad bean (noun)	shell bean plant (noun)
shell beans cooked as lima beans	a bean plant grown primarily for its edible seed rather than its pod
a bean plant cultivated for use animal fodder
Old World upright plant grown especially for its large flat edible seeds but also as fodder
seed of the broad-bean plant