alfalfa vs Medicago sativa

alfalfa and Medicago sativa both are nouns.

Word	Noun	Adjective	Verb	Adverb
alfalfa	Yes	No	No	No
Medicago sativa	Yes	No	No	No

As nouns, alfalfa and Medicago sativa are synonyms defined as:

alfalfa and Medicago sativa: important European leguminous forage plant with trifoliate leaves and blue-violet flowers grown widely as a pasture and hay crop

Other synonyms of alfalfa include lucerne.

alfalfa (noun)	Medicago sativa (noun)
leguminous plant grown for hay or forage	important European leguminous forage plant with trifoliate leaves and blue-violet flowers grown widely as a pasture and hay crop
important European leguminous forage plant with trifoliate leaves and blue-violet flowers grown widely as a pasture and hay crop