Equivalently, the probability that an at-risk individual will acquire a condition.
Point prevalence is a proportion.
A rate is a ratio of the number of events in a group of individuals at risk for the event divided by the total time units contributed by the individuals at-risk of the event and is not a proportion. A numerator divided by a denominator that usually does not include subjects of the numerator and is not restricted to values between 0.0 and 1.0 as are proportions. The rate of onset of a disease in a population per unit time calculated as the number of new cases in a population divided by the total time units each individual in the population was observed before either disease onset occurred in the individual or observation of the individual ceased. Theoretically, incidence is an instantaneous rate. In the population sense, prevalence is the probability at a specific point in time that an individual randomly selected from a group will have the condition, which is equivalent to the proportion of animals in the group that have the disease.