Cornish fowl vs domestic fowl

Cornish fowl and domestic fowl both are nouns.

Word	Noun	Adjective	Verb	Adverb
Cornish fowl	Yes	No	No	No
domestic fowl	Yes	No	No	No

As nouns, domestic fowl is a hypernym of Cornish fowl; that is, domestic fowl is a word with a broader meaning than Cornish fowl:

Cornish fowl: English breed of compact domestic fowl; raised primarily to crossbreed to produce roasters
domestic fowl: a domesticated gallinaceous bird thought to be descended from the red jungle fowl

Other hypernyms of Cornish fowl include fowl, poultry.

Cornish fowl (noun)	domestic fowl (noun)
English breed of compact domestic fowl; raised primarily to crossbreed to produce roasters	a domesticated gallinaceous bird thought to be descended from the red jungle fowl