butter bean vs Phaseolus lunatus

butter bean and Phaseolus lunatus both are nouns.

Word	Noun	Adjective	Verb	Adverb
butter bean	Yes	No	No	No
Phaseolus lunatus	Yes	No	No	No

As nouns, butter bean and Phaseolus lunatus are synonyms defined as:

butter bean and Phaseolus lunatus: bush bean plant cultivated especially in southern United States having small flat edible seeds

Other synonyms of butter bean include butter-bean plant, lima bean, sieva bean.

butter bean (noun)	Phaseolus lunatus (noun)
small flat green bean similar to lima beans	bush bean plant cultivated especially in southern United States having small flat edible seeds
bush bean plant cultivated especially in southern United States having small flat edible seeds