Meaning of AM in English

AM

[am] [ME, fr. OE eom; akin to ON em am, L sum, Gk eimi] pres 1st sing of be AM n, often attrib [amplitude modulation] (1940): a broadcasting system using amplitude modulation; also: a radio receiver of such a system

Merriam-Webster English vocab.      Английский словарь Merriam Webster.