black-eyed pea vs cowpea plant

black-eyed pea and cowpea plant both are nouns.

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

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

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

Other synonyms of black-eyed pea include cowpea, Vigna sinensis, Vigna unguiculata.

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