purple milk vetch vs Astragalus danicus

purple milk vetch and Astragalus danicus both are nouns.

Word	Noun	Adjective	Verb	Adverb
purple milk vetch	Yes	No	No	No
Astragalus danicus	Yes	No	No	No

As nouns, purple milk vetch and Astragalus danicus are synonyms defined as:

purple milk vetch and Astragalus danicus: perennial of southern and western Europe having dense racemes of purple or violet flowers

purple milk vetch (noun)	Astragalus danicus (noun)
perennial of southern and western Europe having dense racemes of purple or violet flowers	perennial of southern and western Europe having dense racemes of purple or violet flowers