Its frequency.

Repetition rate refers to the number of times an event occurs within a specific timeframe, typically measured in cycles per second or Hertz (Hz). In the context of technology or equipment, repetition rate can indicate how quickly a process or function is repeated.

Repetition rate of an AM envelope refers to the frequency of the modulating signal thus the shape of the envelope is identical to the shape of the modulating signal.

repetition rate of signal

The repetition rate of the amplitude modulation (AM) envelope refers to how often the modulation waveform repeats within a given unit of time. It indicates the frequency at which the carrier signal is modulated by the audio signal in an AM transmission. A higher repetition rate results in a faster fluctuation in the amplitude of the carrier signal.