AM

What Does AM Mean in a Text?

The Quick Answer

In relation to time, "am" stands for "ante meridiem," a Latin term meaning "before midday." "AM" can also mean "Amplitude Modulation."

More Details

Ante Meridiem

When used to indicate the time of day, "am" refers to the 12-hour period from midnight (12:00 am) to just before noon (11:59 am), distinguishing it from "pm" ("post meridiem"), which means "after midday" and covers the time from noon to just before midnight. The 12-hour clock system, which uses "am" and "pm" to divide the day, has roots that trace back to ancient civilizations. Both the Egyptians and the Romans divided their days into 12-hour cycles, inspired by the natural cycles of day and night. The adoption of "ante meridiem" and "post meridiem" as terms is credited to the Roman Empire, which had a significant influence on how time was recorded and structured in Western society.

This 12-hour system became more widely standardized during the medieval period in Europe and was solidified with the spread of mechanical clocks in the Renaissance era, which often used the 12-hour format. This format has remained standard in many English-speaking countries, while many other parts of the world prefer the 24-hour clock (e.g., 1000 (10 am), 1400 (2 pm), 2100 (9 pm)) to avoid ambiguity.

Both "am" and "pm" can also be written with periods (full stops) and in uppercase, i.e., "a.m.", "p.m.", "AM", "A.M.", "PM", "P.M.".

Amplitude Modulation

Amplitude Modulation is a technique used in electronic communication for transmitting information via radio waves. In AM, the amplitude (or strength) of a carrier wave is varied in proportion to the waveform of the signal that contains the information. The carrier wave's frequency remains constant, but its amplitude changes to match the signal's changes.

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In relation to time, "am" refers to the 12-hour period from midnight to just before noon.

Summary of Key Points

am
Definition:	Ante Meridiem
Type:	Abbreviation
Guessability:	1: Easy to guess
Typical Users:	Adults and Teenagers

AM
Definition:	Amplitude Modulation
Type:	Abbreviation
Guessability:	5: Extremely difficult to guess
Typical Users:	Specialists

An Academic Look at AM

Example of AM Used in a Text

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