yellow pea vs bush pea

yellow pea and bush pea both are nouns.

Word	Noun	Adjective	Verb	Adverb
yellow pea	Yes	No	No	No
bush pea	Yes	No	No	No

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

yellow pea: western United States bushy herb having yellow pea-like flowers
bush pea: any of various plants of the genus Thermopsis having trifoliate leaves and yellow or purple racemose flowers

yellow pea (noun)	bush pea (noun)
western United States bushy herb having yellow pea-like flowers	any of various plants of the genus Thermopsis having trifoliate leaves and yellow or purple racemose flowers