Also found in: Thesaurus, Medical, Legal, Financial, Acronyms, Encyclopedia, Wikipedia.
n. Abbr. AM
1. The encoding of a carrier wave by varying its amplitude in accordance with an input signal.
2. A broadcast system that uses amplitude modulation.
1. (Telecommunications) one of the principal methods of transmitting audio, visual, or other types of information using radio waves, the relevant signal being superimposed onto a radio-frequency carrier wave. The frequency of the carrier wave remains unchanged but its amplitude is varied in accordance with the amplitude of the input signal. Abbreviation: AM or am Compare frequency modulation
2. (Telecommunications) a wave that has undergone this process
am(æm; unstressed əm, m)
1st pers. sing. pres. indic. of be.
[before 900; Old English am, eam, eom]
1. Asian male.
2. amplitude modulation: a method of impressing a signal on a radio carrier wave by varying its amplitude.
3. a system of broadcasting using this method.Compare FM.
Master of Arts.
[< Latin Artium Magister]
1. before noon.
2. the period from midnight to noon, esp. the period of daylight prior to noon.Compare p.m.
[1755–65; < Latin ante merīdiem]
usage: The abbreviation a.m. refers to the period from midnight until noon. One minute before noon is 11:59 a.m. One minute after noon is 12:01 p.m. Many people distinguish between noon and midnight by saying 12 noon and 12 midnight. Expressions such as 6 a.m. in the morning and 9 p.m. at night are redundant.
A method of radio broadcasting in which the amplitude of the wave that carries the sound signal changes to reflect the various sounds that are to be reproduced, while the frequency of the wave remains the same. Compare frequency modulation.