In epidemiology,<unk>  is a measure of the proportion of people in a population who have a disease or condition at a particular time, such as a particular date. It is like a snap shot of the disease in time. This is in contrast to period<unk>  which is a measure of the proportion of people in a population who have a disease or condition over a specific period of time, say a season, or a year.
Point prevalence
Period prevalence
Cumulative incidence
Biased sample
Number needed to treat
Attributable risk
Prevalence
Sample size