milkweed butterfly vs monarch

milkweed butterfly and monarch both are nouns.

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

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

milkweed butterfly and monarch: 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 butterfly.

milkweed butterfly (noun)	monarch (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
	a nation's ruler or head of state usually by hereditary right