Frequency is defined as:

Frequency is defined as the number of complete wave cycles that pass a point in a given time period, typically measured in seconds. Specifically, it is the measurement of how many waves are produced in one second. This means that for each cycle of the wave that occurs, the frequency counts that occurrence.

When you consider the units, frequency is expressed in hertz (Hz), which is equivalent to one cycle per second. This definition aligns with the concept of the wave in physics, which emphasizes the relationship between time and wave production.

The other definitions provided do not accurately capture this fundamental property of waves. The distance-related suggestion, for example, pertains more to wavelength than to frequency. Similarly, the speed of a wave links to how fast wave energy travels, while the energy aspect discusses the capacity of the wave to do work, which is distinct from the frequency.