Wikipedia has short section for this > Aperiodic frequency is the rate of incidence or occurrence of non-cyclic phenomena, including random processes such as r

Wikipedia has short section for this > Aperiodic frequency is the rate of incidence or occurrence of non-cyclic phenomena, including random processes such as radioactive decay. It is expressed with the unit of reciprocal second (s⁻¹)[14] or, in the case of radioactivity, becquerels.[15] > It is defined as a rate, f = N/Δt, involving the number of entities counted or the number of events happened (N) during a given time duration (Δt);[citation needed] it is a physical quantity of type temporal rate. https://en.wikipedia.org/wiki/Frequency#Aperiodic_frequency https://en.wikipedia.org/wiki/Frequency#Aperiodic_frequency