tall oat grass vs French rye

tall oat grass and French rye both are nouns.

Word	Noun	Adjective	Verb	Adverb
tall oat grass	Yes	No	No	No
French rye	Yes	No	No	No

As nouns, tall oat grass and French rye are synonyms defined as:

tall oat grass and French rye: coarse perennial Eurasian grass resembling oat; found on roadside verges and rough grassland and in hay meadows; introduced in North America for forage

Other synonyms of tall oat grass include Arrhenatherum elatius, evergreen grass, false oat, tall meadow grass.

tall oat grass (noun)	French rye (noun)
coarse perennial Eurasian grass resembling oat; found on roadside verges and rough grassland and in hay meadows; introduced in North America for forage	coarse perennial Eurasian grass resembling oat; found on roadside verges and rough grassland and in hay meadows; introduced in North America for forage