swamphen vs water hen

swamphen and water hen both are nouns.

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

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

swamphen and water 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 swamphen include gallinule, marsh hen.

swamphen (noun)	water 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