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.
2. PM is an acronym for power management.
3. When referring to time, P.M. is short for post meridiem or past midday is the time designated 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 at night.
Should I uppercase or lowercase P.M. in my writing?
The capitalization of P.M. all depends on the style guide you're following and your type of writing. With formal writing and according to the Microsoft Manual of Style you should be using 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 all 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.
5. When referring to maintenance, PM is short for preventive maintenance.
7. When referring to fiber-optic, PM is short for polarization maintaining and is 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.