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If you're familiar with time-telling, you’ve likely come across a.m. and p.m., and you may already be aware that these terms are derived from Latin expressions. But do you know the precise phrases, or their full translation into English?
What exactly do a.m. and p.m. stand for?
As defined by Dictionary.com, a.m. is short for the Latin phrase ante merīdiem, meaning “before midday.” In contrast, p.m. stands for post merīdiem, which means “after midday.” Ever come across someone using “12 m.” or “12:00 m.”? While rare, this is technically the proper way to denote noon. (By the way, noon used to refer to 3 p.m.)
The practice of dividing the day into two 12-hour periods has ancient roots in Latin, and is so old that its origins remain unclear. At the very least, this tradition traces back to the civilizations of ancient Egypt and Mesopotamia.
How should you properly write a.m. and p.m.?
When writing a.m. or p.m. in formal contexts—such as in academic papers, published articles, or even a fan letter to your favorite Mytour author—it’s best to use lowercase letters and include periods, as we’ve done in this article. However, as noted by Dictionary.com, using “am/pm” or “AM/PM” is acceptable elsewhere, as long as you remain consistent.
Latin is present everywhere—from legal terms and medical diagnoses to Harry Potter spells—and it’s more embedded in our daily lives than we often realize. We also unknowingly speak countless words borrowed from this so-called dead language. If this article has sparked an interest in exploring more Latin abbreviations, you can begin here with the often-misunderstood distinction between “i.e.” and “e.g.”
Are there alternative ways to express “a.m.” and “p.m.”?
If using “a.m.” or “p.m.” feels a bit dull, you might enjoy a bit of slang from the 1910s: Telephone operators in the early 20th century used pip emma to mean p.m. and ack emma to mean a.m. For instance, if someone said they planned to catch the train at seven o’clock pip emma, they were referring to 7 p.m. Eventually, these phrases—originally from the military, according to Green’s Dictionary of Slang—became common alternatives to afternoon and morning.
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