prevalence (Noun) — The quality of prevailing generally; being widespread. ex. "he was surprised by the prevalence of optimism about the future"
prevalence (Noun) — (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.
prevalence (Noun) — A superiority in numbers or amount. ex. "a prevalence of evidence against the defendant"