greengage vs greengage plum

greengage and greengage plum both are nouns.

Word	Noun	Adjective	Verb	Adverb
greengage	Yes	No	No	No
greengage plum	Yes	No	No	No

As nouns, greengage and greengage plum are synonyms defined as:

greengage and greengage plum: sweet green or greenish-yellow variety of plum

greengage (noun)	greengage plum (noun)
sweet green or greenish-yellow variety of plum	sweet green or greenish-yellow variety of plum