pigweed vs lamb's-quarters

pigweed and lamb's-quarters both are nouns.

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

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

pigweed and lamb's-quarters: common weedy European plant introduced into North America; often used as a potherb

Other synonyms of pigweed include Chenopodium album, wild spinach.

pigweed (noun)	lamb's-quarters (noun)
leaves collected from the wild	common weedy European plant introduced into North America; often used as a potherb
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