Ante meridiem

Ante meridiem (often abbreviated as AM or a.m.) is a Latin phrase used to denote the period of the day from midnight to noon. The term is part of the 12-hour clock system, which is commonly used in English-speaking and other countries that do not use the 24-hour clock system.

Etymology

The term "ante meridiem" is derived from Latin, where "ante" means "before" and "meridiem" means "midday" or "noon". Thus, the term literally translates to "before midday".

Usage

In the 12-hour clock system, the day is divided into two periods: ante meridiem (a.m.) and post meridiem (p.m.). The a.m. period starts at midnight (00:00) and ends just before noon (11:59). Therefore, all times between midnight and noon are typically denoted with "a.m." in written and digital communication.

Cultural Variations

While the use of the 12-hour clock and the terms "a.m." and "p.m." are widespread, there are cultural variations. For example, in many Spanish-speaking countries, the terms "de la mañana" (in the morning), "de la tarde" (in the afternoon), and "de la noche" (in the evening/night) are used instead of "a.m." and "p.m.".

Confusion and Ambiguity

The use of the 12-hour clock can lead to confusion and ambiguity, particularly in regards to the start of the day. For example, 12:00 a.m. is often considered the start of the day, but can be interpreted as midnight at the start or end of a day. To avoid this confusion, many airlines, railroads, and other transport services use the 24-hour clock.

See Also

• 12-hour clock
• 24-hour clock
• Post meridiem