erythema vs erythroderma

erythema and erythroderma both are nouns.

Word	Noun	Adjective	Verb	Adverb
erythema	Yes	No	No	No
erythroderma	Yes	No	No	No

As nouns, erythroderma is a hypernym of erythema; that is, erythroderma is a word with a broader meaning than erythema:

erythema: abnormal redness of the skin resulting from dilation of blood vessels (as in sunburn or inflammation)
erythroderma: any skin disorder involving abnormal redness

erythema (noun)	erythroderma (noun)
abnormal redness of the skin resulting from dilation of blood vessels (as in sunburn or inflammation)	any skin disorder involving abnormal redness