pigeon pea vs pea

pigeon pea and pea both are nouns.

Word	Noun	Adjective	Verb	Adverb
pigeon pea	Yes	No	No	No
pea	Yes	No	No	No

As nouns, pea is a hypernym of pigeon pea; that is, pea is a word with a broader meaning than pigeon pea:

pigeon pea (noun)	pea (noun)
small highly nutritious seed of the tropical pigeon-pea plant	seed of a pea plant used for food
tropical woody herb with showy yellow flowers and flat pods; much cultivated in the tropics	a leguminous plant of the genus Pisum with small white flowers and long green pods containing edible green seeds
	the fruit or seed of a pea plant