milk vetch vs woody plant

milk vetch and woody plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
milk vetch	Yes	No	No	No
woody plant	Yes	No	No	No

As nouns, woody plant is a hypernym of milk vetch; that is, woody plant is a word with a broader meaning than milk vetch:

milk vetch: any of various plants of the genus Astragalus
woody plant: a plant having hard lignified tissues or woody parts especially stems

Other hypernyms of milk vetch include ligneous plant.

milk vetch (noun)	woody plant (noun)
any of various plants of the genus Astragalus	a plant having hard lignified tissues or woody parts especially stems