American coot vs marsh hen

American coot and marsh hen both are nouns.

Word	Noun	Adjective	Verb	Adverb
American coot	Yes	No	No	No
marsh hen	Yes	No	No	No

As nouns, American coot and marsh hen are synonyms defined as:

Other synonyms of American coot include Fulica americana, mud hen, water hen.

American coot (noun)	marsh hen (noun)
a coot found in North America	any of various small aquatic birds of the genus Gallinula distinguished from rails by a frontal shield and a resemblance to domestic hens
	a coot found in North America