Real Dictionary

a.m.
a.m. is used after a number to show that you are referring to a particular time between midnight and noon. Compare p.m.

a.m. in American English
abbreviation
adverb: before noon
noun: the period from midnight to noon, esp. the period of daylight prior to noon

a.m. in British English
abbreviation for: ante meridiem

am
AM is a method of transmitting radio waves that can be used to broadcast sound. AM is an abbreviation for 'amplitude modulation'.
Am is the first person singular of the present tense of be1. Am is often shortened to 'm in spoken English. The negative forms are 'I am not' and 'I'm not'. In questions and tags in spoken English, these are usually changed to 'aren't I'.
countable noun: An AM is a member of the Welsh Assembly. AM is an abbreviation for 'assembly member'.

am in American English
be
abbreviation: amplitude modulation: a method of impressing a signal on a radio carrier wave by varying its amplitude
the chemical symbol for: americium
verb

AM in American English 1
America
amplitude-modulation broadcasting or sound transmission, characterized by the capability of transmitting over long distances and by a moderate to high level of noise and static

AM in American English 2
americium
amplitude modulation

Am in British English
abbreviation for: associate member
the chemical symbol for: americium

am in British English 1
verb

am in British English 2
abbreviation for

am in British English 3
the internet domain name for: Armenia

Am.
Am. is a written abbreviation for American.

Am. in American English
abbreviation: America

Am. in British English
abbreviation for: America(n)

Armenia in British English 3
noun: a republic in NW Asia: originally part of the historic Armenian kingdom; acquired by Russia in 1828; became the Armenian Soviet Socialist Republic in 1936; gained independence in 1991. It is mountainous, rising over 4000 m (13 000 ft). Language: Armenian.