pigweed vs lamb's-quarter

pigweed and lamb's-quarter both are nouns.

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

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

Other synonyms of pigweed include wild spinach.

pigweed (noun)	lamb's-quarter (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