PM (or p.m.) is an abbreviation of the Latin phrase post meridiem , which means "after noon" or "after midday." It is used in the 12-hour clock system to indicate the time from 12:00 noon to 11:59 at night

. In the 12-hour clock:

• AM (ante meridiem) covers the time from midnight (12:00 a.m.) to just before noon (11:59 a.m.).
• PM (post meridiem) covers the time from noon (12:00 p.m.) to just before midnight (11:59 p.m.).

Noon is designated as 12:00 p.m., and midnight as 12:00 a.m., though these can sometimes cause confusion, so it is often clearer to say "12 noon" or "12 midnight"

. Additionally, "PM" can have many other meanings depending on context, such as:

• Prime Minister (politics)
• Project Manager (business)
• Particulate Matter (environmental science, referring to tiny particles in the air)
• Various scientific, technological, and cultural uses

But in the context of time, PM specifically refers to the afternoon and evening hours after 12 noon until midnight.