water hen vs marsh hen

water hen and marsh hen both are nouns.

Word	Noun	Adjective	Verb	Adverb
water hen	Yes	No	No	No
marsh hen	Yes	No	No	No

As nouns, water hen and marsh hen are synonyms defined as:

water hen and marsh hen: any of various small aquatic birds of the genus Gallinula distinguished from rails by a frontal shield and a resemblance to domestic hens

Other synonyms of water hen include gallinule, swamphen.

As nouns, water hen and marsh hen are synonyms defined as:

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

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