roseola vs eruption

roseola and eruption both are nouns.

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

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

roseola (noun)	eruption (noun)
any red eruption of the skin	the sudden occurrence of a violent discharge of steam and volcanic material
	a sudden very loud noise
	the emergence of a tooth as it breaks through the gum
	a sudden violent spontaneous occurrence (usually of some undesirable condition)
	(of volcanoes) pouring out fumes or lava (or a deposit so formed)
	symptom consisting of a breaking out and becoming visible