Updated: 08/02/2020 by Computer Hope

AM may refer to any of the following:

Dial turned to FM

1. With audio or a signal, AM is short for amplitude modulation. AM is a broadcast capable of broadcasting in a wide area, but in a lower quality compared to FM (frequency modulation).

2. With time, A.M. is short for ante meridiem, which is Latin for "before the middle of the day" and can also mean "after midnight." This time is between 11:59 P.M. midnight and 11:59 P.M. noon. In other words, A.M. is in the morning and P.M. is in the afternoon and at night.


When handling military time (00:00-24:00) A.M. and P.M. are not used.

Should I uppercase or lowercase A.M. in my writing?

The capitalization of A.M. depends on the style guide you're following and your type of writing. With formal writing and according to the Microsoft Manual of Style use uppercase and include periods, as we've done on this page. Other style guides like the AP Stylebook, Chicago Manual of Style, and Merriam-Webster's Collegiate Dictionary all recommend writing a.m. as lowercase with periods.

If you're writing for a company or organization, follow their style guide or the rules in the style guide they follow. If no style guide is followed decide on one form of style and be consistent in all your writing.

Should I use periods when writing A.M. in my writing?

As with the capitalization of A.M., using periods or omitting periods depends on the style guide you're following or personal preference. Many people use periods because "am" is a word by itself and using it with time may introduce confusion. Others prefer the look and ease of writing "am" without periods.

3. On the Internet, .am is a top-level domain for Armenia.

Computer acronyms, FM, Hardware terms, PM, Radio, Wireless