What type of modulation varies the instantaneous power level of the RF signal?

Amplitude modulation (AM) is the process of conveying information by varying the amplitude (or strength) of the carrier wave. Because a signal's power is proportional to the square of its voltage amplitude, changing the amplitude directly causes the instantaneous power level of the RF signal to fluctuate. In contrast, Frequency Modulation (FM) and Phase Modulation (PM) are constant-envelope modes, meaning their peak amplitude and average power levels remain constant while only the frequency or phase changes. "Power modulation" is a distractor term intentionally made up for this question.