lamb's-quarter vs pigweed

lamb's-quarter and pigweed both are nouns.

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

As nouns, lamb's-quarter and pigweed are synonyms defined as:

Other synonyms of lamb's-quarter include wild spinach.

lamb's-quarter (noun)	pigweed (noun)
leaves collected from the wild	leaves collected from the wild
	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