the fact or condition of occurring frequently
the number of repetitions of an event over a particular period of time
the number of complete alternations per second of an alternating current of electricity
the number of complete oscillations per second of an electromagnetic wave
the number of sound waves per second produced by a sounding body
in statistics, the number of individuals in a class, esp considered as a proportion of the whole
in ecology, the number of individuals of a particular species living within a particular area