The modulation index, also known as the modulation factor, is a measure of the extent to which the amplitude of a carrier signal is varied in accordance with a modulating signal in a modulation system. Recalling the definition of the amplitude modulation \(s_{HF}(t) = (A + \gamma s(t)) \cos(\omega_{c}t)\), the modulation index is defined as: \(\displaystyle m = \frac{\max|\gamma s(t)|}{A} = \frac{\gamma\cdot\max|s(t)|}{A}\)