pigweed vs leafy vegetable

pigweed and leafy vegetable both are nouns.

Word	Noun	Adjective	Verb	Adverb
pigweed	Yes	No	No	No
leafy vegetable	Yes	No	No	No

As nouns, leafy vegetable is a hypernym of pigweed; that is, leafy vegetable is a word with a broader meaning than pigweed:

pigweed: leaves collected from the wild
leafy vegetable: any of various leafy plants or their leaves and stems eaten as vegetables

Other hypernyms of pigweed include green, greens.

pigweed (noun)	leafy vegetable (noun)
leaves collected from the wild	any of various leafy plants or their leaves and stems eaten as vegetables
common weedy European plant introduced into North America; often used as a potherb
leaves sometimes used as potherbs; seeds used as cereal; southern United States to Central America; India and China