swallowtail vs morning coat

swallowtail and morning coat both are nouns.

Word	Noun	Adjective	Verb	Adverb
swallowtail	Yes	No	No	No
morning coat	Yes	No	No	No

As nouns, swallowtail and morning coat are synonyms defined as:

swallowtail and morning coat: a man's full-dress jacket with two long tapering tails at the back

Other synonyms of swallowtail include swallow-tailed coat.

swallowtail (noun)	morning coat (noun)
a man's full-dress jacket with two long tapering tails at the back	a man's full-dress jacket with two long tapering tails at the back