lamb's-quarter vs greens

lamb's-quarter and greens both are nouns.

Word	Noun	Adjective	Verb	Adverb
lamb's-quarter	Yes	No	No	No
greens	Yes	No	No	No

As nouns, greens is a hypernym of lamb's-quarter; that is, greens is a word with a broader meaning than lamb's-quarter:

lamb's-quarter: leaves collected from the wild
greens: any of various leafy plants or their leaves and stems eaten as vegetables

Other hypernyms of lamb's-quarter include green, leafy vegetable.

lamb's-quarter (noun)	greens (noun)
leaves collected from the wild	any of various leafy plants or their leaves and stems eaten as vegetables