butter bean vs butterbean

butter bean and butterbean both are nouns.

Word	Noun	Adjective	Verb	Adverb
butter bean	Yes	No	No	No
butterbean	Yes	No	No	No

As nouns, butter bean and butterbean are synonyms defined as:

Other synonyms of butter bean include civet bean, sieva bean.

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