hives vs roseola

hives and roseola both are nouns.

Word	Noun	Adjective	Verb	Adverb
hives	Yes	No	No	No
roseola	Yes	No	No	No

As nouns, roseola is a hypernym of hives; that is, roseola is a word with a broader meaning than hives:

hives: an itchy skin eruption characterized by weals with pale interiors and well-defined red margins; usually the result of an allergic response to insect bites or food or drugs
roseola: any red eruption of the skin

Other hypernyms of hives include efflorescence, rash, skin rash, hypersensitivity reaction.

hives (noun)	roseola (noun)
an itchy skin eruption characterized by weals with pale interiors and well-defined red margins; usually the result of an allergic response to insect bites or food or drugs	any red eruption of the skin