epidemiology vs prevalence

epidemiology and prevalence both are nouns.

Word	Noun	Adjective	Verb	Adverb
epidemiology	Yes	No	No	No
prevalence	Yes	No	No	No

epidemiology (noun)	prevalence (noun)
the branch of medical science dealing with the transmission and control of disease	the quality of prevailing generally; being widespread
	a superiority in numbers or amount
	(epidemiology) the ratio (for a given time period) of the number of occurrences of a disease or event to the number of units at risk in the population