Updated: 01/18/2023 by Computer Hope

PM may refer to any of the following:

1. In chat, PM is short for private message or personal message and is a message only sent between you and another user.


Services like Discord, Instagram, Twitter, and Facebook use DM (direct message) instead of PM, although they have the same meaning.

2. PM is an acronym for power management.

3. With time, P.M. is short for post meridiem or past midday and is the time after 11:59 A.M. and before 12:00 A.M. midnight. In other words, A.M. is in the morning, and P.M. is in the afternoon and night.


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

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

The capitalization of P.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 P.M. in my writing?

As with the capitalization of P.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.

4. With OS/2 or an operating system, PM is short for Presentation Manager.

5. When describing maintenance, PM is short for preventive maintenance.

6. With a waveform or a signal, PM is short for phase modulation. PM is a method of encoding and transmitting information in a carrier wave to transmit data wirelessly.

7. With fiber-optic, PM is short for polarization maintaining, also known as PMF or polarization maintaining fiber. PM or PMF is an optical fiber that maintains a fixed polarization to help increase the bandwidth and distance of how far the signal can travel.

8. The Internet domain suffix .pm is short for St. Pierre and Miquelon.

AM, Chat terms, Computer acronyms, DM, FM, Operating system terms, Phase, Presentation Manager, Preventive Maintenance, Time, Whisper