Rate
A rate is a ratio of a frequency to a potential frequency, multiplied by a standard size. That is:
where X is some frequency of interest, Y is the potential total frequency of X, and S is some standard size.
For example, we can calculate the fertility rate for a community as the number of live births (X) divided by the number of women of childbearing age (Y) multiplied by 1,000 (S).
It is important to remember that rates describe places, not people. People can give birth or commit crimes; these are individual events. Rates describe the frequency of these events in a particular place.