purple gallinule vs swamphen

purple gallinule and swamphen both are nouns.

Word	Noun	Adjective	Verb	Adverb
purple gallinule	Yes	No	No	No
swamphen	Yes	No	No	No

As nouns, swamphen is a hypernym of purple gallinule; that is, swamphen is a word with a broader meaning than purple gallinule:

purple gallinule: gallinules with showy purplish plumage
swamphen: any of various small aquatic birds of the genus Gallinula distinguished from rails by a frontal shield and a resemblance to domestic hens

Other hypernyms of purple gallinule include gallinule, marsh hen, water hen.

purple gallinule (noun)	swamphen (noun)
gallinules with showy purplish plumage	any of various small aquatic birds of the genus Gallinula distinguished from rails by a frontal shield and a resemblance to domestic hens