leaf mustard vs mustard greens

leaf mustard and mustard greens both are nouns.

Word	Noun	Adjective	Verb	Adverb
leaf mustard	Yes	No	No	No
mustard greens	Yes	No	No	No

As nouns, leaf mustard and mustard greens are synonyms defined as:

Other synonyms of leaf mustard include Indian mustard, mustard.

leaf mustard (noun)	mustard greens (noun)
leaves eaten as cooked greens	leaves eaten as cooked greens
Asiatic mustard used as a potherb