AM

I. noun Usage: often attributive Etymology: amplitude modulation Date: 1940 a broadcasting system using amplitude modulation; also a radio receiver of such a system II. abbreviation 1. airmail 2. Air Medal 3. [Latin anno mundi] in the year of the world — often printed in small capitals 4. ante meridiem — often not cap and often punctuated 5. [New Latin artium magister] master of arts