Cornish heath vs true heath

Cornish heath and true heath both are nouns.

Word	Noun	Adjective	Verb	Adverb
Cornish heath	Yes	No	No	No
true heath	Yes	No	No	No

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

Cornish heath: bushy shrub having pink to white flowers; common on the moors of Cornwall and in southwestern Europe; cultivated elsewhere
true heath: any plant of the genus Erica

Other hypernyms of Cornish heath include erica.

Cornish heath (noun)	true heath (noun)
bushy shrub having pink to white flowers; common on the moors of Cornwall and in southwestern Europe; cultivated elsewhere	any plant of the genus Erica