# Aperiodic frequency

**Aperiodic frequency** is the rate of incidence or occurrence of non-cyclic phenomena, including random processes such as radioactive decay. It is expressed in units of measurement of reciprocal seconds (s^{−1})[1] or, in the case of radioactivity, becquerels.[2]

It is defined as a ratio, *f* = *N*/*T*, involving the number of times an event happened (*N*) during a given time duration (*T*); it is a physical quantity of type temporal rate.

## See also

## References

- Lombardi, Michael A. (2007). "Fundamentals of Time and Frequency". In Bishop, Robert H. (ed.).
*Mechatronic Systems, Sensors, and Actuators: Fundamentals and Modeling*. Austin: CRC Press. ISBN 9781420009002. - "Units with special names and symbols; units that incorporate special names and symbols".
*SI Brochure: The International System of Units (SI)*(8th ed.). Section 2.2.2. 2014.

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