It is a shortened form of radiotelegraph - apparatus for transmitting or receiving radio broadcasts. Derived from Radiophone and Radiotelography, words coined in the 1890's
AM on a radio stands for amplitude modulation.
Radio
Alpha
RAdio Detecting And Ranging
Amplitude Modulation
Amplitude modulation.
Tela
Radio wave fequency....
AM stans for "Amplitude modulation"
Radio
Delta
Prgenet radio corn