:::I understand.  However, the modified definition should not be interpreted that way.  It's not saying that every device for increasing the amplitude of a signal is an amplifier, just that an amplifier is a device for increasing the amplitude of a signal.  Sometimes the power level is quite irrelevant in amplifiers used to process signals, and a power increase may not exist at every amplifier circuit, even if the circuit is capable of providing an output signal of more power than the input signal.