cowpea plant vs black-eyed pea

cowpea plant and black-eyed pea both are nouns.

Word	Noun	Adjective	Verb	Adverb
cowpea plant	Yes	No	No	No
black-eyed pea	Yes	No	No	No

As nouns, cowpea plant and black-eyed pea are synonyms defined as:

cowpea plant and black-eyed pea: sprawling Old World annual cultivated especially in southern United States for food and forage and green manure

Other synonyms of cowpea plant include cowpea, Vigna sinensis, Vigna unguiculata.

cowpea plant (noun)	black-eyed pea (noun)
sprawling Old World annual cultivated especially in southern United States for food and forage and green manure	eaten fresh as shell beans or dried
	sprawling Old World annual cultivated especially in southern United States for food and forage and green manure
	fruit or seed of the cowpea plant