The 12-hour clock is a time convention in which the 24 hours of the day are divided into two periods: a.m. (from Latin ante meridiem, translating to before midday. What Do AM and PM Stand For? By Aparna Kher and Konstantin Bikos Some countries use the 12-hour clock format with “am” and “pm” labels. What do these abbreviations mean? Is midnight am or pm? Book your train and bus tickets today by choosing from over 30 U.S. train routes and 500 destinations in North America. AM and PM denote whether it is before or after the middle of a day. In our article we explain the difference with 24-hour clock and different tips on how to use, spell and understand AM and PM. AM = Before noon (morning hours) in time notation. AM = Latin for “before midday” (historical origin). AM has specialized meanings in physics, finance, and online culture. Always use AM/PM correctly to avoid confusion in writing and scheduling. The abbreviation is here to stay, even as the world shifts toward 24-hour clocks. Next time you see AM, you’ll know exactly what it means. Find out the full form and meaning of am and pm. Learn more about their conversions to the 24-hour clock using conversion tips, solved examples, and practice questions. Learn what is am and pm in the 12-hour clock system. AM means before midday and PM means after. Master time telling with simple rules and examples. AM/PM in Digital Devices Most smartphones and operating systems store time using the 24-hour clock internally. The AM/PM display is a formatting choice. Your day is defined by the split between morning and night. But while you use a.m. vs. p.m. regularly, do you know what they really mean? Free shipping on millions of items. Get the best of Shopping and Entertainment with Prime. Enjoy low prices and great deals on the largest selection of everyday essentials and other products, including fashion, home, beauty, electronics, Alexa Devices, sporting goods, toys, automotive, pets, baby, books, video games, musical instruments, office supplies, and more.