field pea vs Pisum arvense

field pea and Pisum arvense both are nouns.

Word	Noun	Adjective	Verb	Adverb
field pea	Yes	No	No	No
Pisum arvense	Yes	No	No	No

As nouns, field pea and Pisum arvense are synonyms defined as:

field pea and Pisum arvense: variety of pea plant native to the Mediterranean region and North Africa and widely grown especially for forage

Other synonyms of field pea include Austrian winter pea, field-pea plant, Pisum sativum arvense.

field pea (noun)	Pisum arvense (noun)
coarse small-seeded pea often used as food when young and tender	variety of pea plant native to the Mediterranean region and North Africa and widely grown especially for forage
variety of pea plant native to the Mediterranean region and North Africa and widely grown especially for forage
seed of the field pea plant