milkweed butterfly vs monarch butterfly

milkweed butterfly and monarch butterfly both are nouns.

Word	Noun	Adjective	Verb	Adverb
milkweed butterfly	Yes	No	No	No
monarch butterfly	Yes	No	No	No

As nouns, milkweed butterfly and monarch butterfly are synonyms defined as:

milkweed butterfly and monarch butterfly: large migratory American butterfly having deep orange wings with black and white markings; the larvae feed on milkweed

Other synonyms of milkweed butterfly include Danaus plexippus, monarch.

milkweed butterfly (noun)	monarch butterfly (noun)
large migratory American butterfly having deep orange wings with black and white markings; the larvae feed on milkweed	large migratory American butterfly having deep orange wings with black and white markings; the larvae feed on milkweed